PowerPC desktop Mac black screen fault?

Question: Since upgrading to Yosemite, the screen on our PowerPC desktop Mac is totally black and the light on the bottom right of the monitor flashes 'dot dash dot' repeatedly. We can't seem to find a solution having tried the obvious e.g switching off and on again. Please can anyone help?
Comment: Not being pedantic but Yosemite doesn't run on the PowerPC architecture, it's Intel only. What specific model of Mac is it? If your monitor's indicating an issue the chances are it's a sync out-of-range warning (it's being fed a signal which it can't display). Try restarting in safe-boot, hold shift down when the the Mac chimes and see if this helps.
Comment: Thanks very much for your answer. I will check it later today when back home :-)
Answer: PowerPC based Macs are old, too old to run Yosemite by a good number of years so I'm going to guess that you have a MacPro and an Apple Cinema Display in which case:
http://support.apple.com/en-us/ht2811
Should help.
Edit:
I should expand on my rather terse answer. I think that the timing of you upgrading to Yosemite is a bit of a red herring. The problem according to the KB article seems to be to do with the power supply. It may have been damaged in some way (or maybe just 'got old'). Check everything is plugged in snugly and that nothing is shorting (no hissy-poppy-crackeling sounds). Also check for excessive heat coming from the power adapter. It shouldn't be too hot to hold, if it is it implies some form of damage.
~W

PowerPC desktop Mac black screen fault?


How to change my character religion?

Question: My character is with pagan religion (Tengri) and I want to convert him to Orthodox Christianity? How do I do that?
Answer: There are two ways for you to change religions. The first is to select the religion you wish to change to (use the Religious map mode, R), and hit the "Convert" button. This has a piety cost based on a number of factors (mostly how similar the religions are to one-another, but factors like whether it's been reformed are also factors).

The other option is to adopt the religion of a spouse or concubine. This is "free", but you do need to be married in the first place, which can be dicey, especially if the religion you're hoping to convert to is considered "evil" in the eyes of your current one, which can cause an opinion malus large enough to prevent marriage in the first place.
Once you're legally tied to your heretical partner, simply choose "Adopt Faith" from the interaction menu.
Comment: For underage heirs, you can assign a Ward and ask the ward to convert your heir. Although it's not strictly "your character" at that point in time, it will likely be "you" somewhere in the future.
Comment: Another option is that when you are being attacked in a Holy War, then there is a decision available to end the war by converting to the religion of the attacker. But that's of course very situational.
Comment: Lol I've just noticed it doesn't logically make much sense to require you to be very pious in order to be able to change religion. In-universe, if you managed to acquire so much faith, you would (usually) be _less_ likely to do such a thing…

How to change my character religion?


How to use Gigabit Ethernet with MCU?

Question: I am new at ethernet and it comes complex. Trying to use STM32's RMII interface with switch. I just want to see at IT's switch gigabit port. I don't want to transfer data gigabit, it doesn't matter. Some gigabit switches doesn't see megabit ports. If i choose RMII, RGMII supporting PHY will switch or computer see as gigabit ethernet?
Comment: *Some gigabit switches doesn't see megabit ports*: replace these switches. There's little excuse for that; there is valid reasons why your hardware needs to support Gigabit-only (namely, large frames can be crucial for some data streaming applications, even if the net rate stays significantly < 1Gb/s), but on the switch side, that's just strange.
Answer: The gigabit PHY would have to say it supports RMII in the datasheet. If it's not explicit you might ask the company but just because it supports RGMII does not mean it's backwards compatible.
I've also seen network devices support RGMII and RMII but not MII so it's important to check.
In the datasheet of the KSZ9563RNXC it says:

One port with 10/100/1000 Ethernet MAC with RMII/MII/RGMII interface.

So the STM32 could connect via RGMII and 10/100. It won't make sense for the STM32 to connect faster than that, because it can't handle the bandwidth of a 1000TX link.
Answer: If your MCU has no gigabit interface (GMII/RGMII) then you don't have gigabit interface to the PHY and then the PHY can't form a gigabit link either.
If you have only MII/RMII then only 100Mbps link can be formed with MCU.
But the picture in your question has a switch chip with two gigabit PHYs and separate MCU interface so the gigabit ports can form gigabit links even if RMII/MII port is used with MCU, because they are completely separate.

How to use Gigabit Ethernet with MCU?


Can you save everyone in Haven?

Question: During the invasion, you are tasked with rescuing several people. However, no matter how many times I try, I can never seem to save them all. Is this intended or am I doing something wrong?
Answer: Can be done, even on Nightmare. It is imperative that you follow a fairly precise route, though.

Clear the doorway at the forge so Harritt can get his things.
Enter the gates and turn right to save Lysette.
Head back the way you came and go up the next set of stairs. Wait for the enemies to come to you to avoid starting the timer for Flissa.
Head into the tavern by the closest door and rescue Flissa. Ignore enemies when you do this.
Head back out by the same door. Do NOT use the door next to Flissa -- you'll trigger the explosive pots too soon. You can now finish off the enemies near the tavern but stay away from the pots area.
Then, head straight up the path towards the pots. Rescue Adan first, then Minaeve. It can be done, but it is a very narrow window.
Then go to the requisitions area and rescue the woman (Threnn) there.
Head back down the stairs to save Seggrit from the burning building. The door is blocked so you'll have to climb a ladder and jump over to the log piles and jump inside the building.

The key thing is to avoid entering the trigger area until you're ready. As soon as you hit the trigger boundary, one of your companions will say they hear a survivor. When that happens, drop everything and run to the rescue.
Comment: Just re-did the quest on my second playthrough, worked like a charm.
Comment: With Seggrit's building, I just smashed the door down with my mace. Worked fine.
Comment: In addition to (6), you can send party members to both Adan and Minaeve (set them to hold position), and then you can jump from one party member to the other instead of running around the pots. This gives you 1-2 seconds of leeway.
Answer: It is possible, but you seriously need to be quick on your feet. For the woman in the tavern and the two up by the eastern side, you just need to completely disregard the enemies and rush to save them before they die, because their timers are really short. Then for Threnn up at the Chantry, you just need to keep her alive as best as you can in the fight, and then for the guy down in the burning house, you need to break the door open. The key is not triggering them until you're ready to save them since their timers don't start until they become an objective.
Answer: Try to use the tactical camera to save Flissa, Minaeve and Adan using your party members at the same time (you need to ignore the enemies). Careful not to go with the left stair near the tavern as it will trigger saving Threnn quest. The right stair won't trigger it, save Seggrit last by using the ladder to go inside his house.
Some of the party members will say we rallied everyone or something similar if you have saved all of them.
Answer: I followed Jonathan Fingland's route and it worked, although you don't actually save everyone by reviving them manually. This is the case for Lysette and Threnn, who apparently are well enough to fight with you. Pause and use tactical screen to view them, they will also greet you once the fight is over before running for the Chantry, and that tells you they survived the fight.
Answer: My method was this (and best to use one of each class in party for the whole game)

Harrit, use a warrior and smash boxes
Lysette
Segrrit, again warrior to smash boxes
Flissa
Adan
Minaeve
Therrn

I have noticed a glitch when both using tactical camera, and not using it. (Note: I play on the PS3).
Sometimes you have to click twice on the person to actually save them. This is a pain when trying to save Adan and Minaeve.
My suggestion is to save after saving Flissa in the tavern. That way you can redo it if you fail both.
Answer: I don't think so. Me and a mate are playing through at the same time, roughly same stats etc., and we could only save the woman in the burning building (Flissa) then Lysette (the Templar  woman) and the two guys just before you get forced into the main base bit. The healer woman seemed to die from the explosions regardless of how fast you got to her but I'm still not sure if that's scripted.
I don't think you can save anyone else though, I did try looking for the horse master guy but I think he's one of the dead outside the pen.
Using revive on her does not work either, it's a manual revive regardless of class.
Tried by me and my mate
Comment: No, it's absolutely possible to help Harritt and save every one else (all 6 of them).

Can you save everyone in Haven?


Windows 7 RC netbook not waking up for nightly WHS backup

Question: What could be causing my MSI Wind U120 netbook running Windows 7 RC not to wake up from sleep for its nightly Windows Home Server backup?  I have two other machines, an Acer laptop and a desktop, that are backing up normally, but they're running Vista.
Answer: It might be your wake on lan settings in your bios, this needs to be enabled.
Answer: For all machines, check your BIOS power settings to ensure Wake on LAN is enabled.
If you are planning on using the wireless cards to enact Wireless Wake on LAN you also have to ensure the BIOS can even support this function.
Comment: Most don't, keeping the WiFi on for WoL is a great way to make sure that your battery will be drained when you go to use it.
Comment: I'm in agreement.  I get a few clients who complain about their battery life and don't realize this is why.
Comment: I'll check on this -- thanks.  Both laptops typically stay plugged in overnight so battery life isn't much of an issue.
Answer: I know that this is old now, but WHS does NOT use WOL for backups.
When the machine is on, it talks to WHS and finds out what the backup window, and then schedules a time to wake up. Once awake, the machine will check if it's running on batteries. If it is, it will put the machine to sleep (even if it was hibernating). If not it will jump in to a queue for a WHS backup.
Once complete, it will put the machine to sleep (again, even if it was hibernating).
As for this question, check the WHS Tray app is marked to "Wake This Computer for Backup" and that it is plugged in to power.
Answer: Unfortunately the BIOS for this machine doesn't let me access any Wake on LAN settings.
However I was looking through the power options and found that it was set to hibernate after an hour of sleep.  I disabled hibernation and now the backups seem to be running normally.
Answer: Wake on LAN has nothing to do with the OS.  As the other have stated you need to check the BIOS and NIC support this feature (and have it turned on)


Naming pattern for model which access multiple tables

Question: What I know is that, We name model having table name.
But what about the model which access multiple table.
What should be the naming standard for them?
Comment: what to you mean by a module? Is it a model class or something? Are you using entity framework?
Comment: sorry writing mistake it was model class.
Answer: Assuming that you mean in the context of a MVC pattern, the Model is outward facing, for manipulation by the Controller and consumption by the View. The names of Model classes should be chosen to help the authors of View and Controller. I don't agree that the names of an implementation detail of the Model (the database tables) is necessarily the correct basis for the names of the Model classes.
To take a simple example: Suppose we have a CUSTOMER table. Then we create a Customer class, all very nice we understand it perfectly. Now suppose that for performance reasons (In this contrived example, unlikely, but in real systems with legacy databases it happens) perhaps for the benefit of a completely different system,  we decide to create a CUSTOMER_SUMMARY table containing only a few of the columns, and a CUSTOMER_DETAILS table, containing all the rest of the columns. Should we now rename our Customer class?  It takes data from both tables, so we no longer conform to our naming convention, but from the perspective of the View it is the Customer data, it's just what they need. I say "no", the name is exactly correct, the implementation detail has changed, but that is not important to our consumers.
Similarly, if we have ORDERS, ORDER_LINES, PRODUCTS and a class that holds the information about an Order, which is likely to take data from all three tables, I'd call that class Order. If in the future I need summary data taken from ORDERS only I might us a Class OrderSummary. I try to choose a name that is easy to understand from the "outside".
Answer: I think there is no straight forward naming conventions as such. you can use the real domain name for your model according to your business. Let say you want to map AddressInfo, Street , City tables  in to one model (domain) class then the name will be something like Address.
Other than that mapping several tables for one model (Domain ) class is not a good practice in entity Framework. Because it will generate very complex queries which reduces the performance


What is the remainder when a polynomial $g(x^{12})$ is divided by $g(x)$?

Question: Let $g(x) = x^5 +x^4 +x^3+x^2+x+1$.
What is the remainder when the polynomial $g(x^{12})$ is divided by the polynomial $g(x)$?
Comment: Note that if $t\ne 1$ then $g(t)=\frac{t^6-1}{t-1}$.
Answer: HINT :
$$g(x)=x^5+x^4+x^3+x^2+x+1=\frac{x^6-1}{x-1}$$
for $x\not=1$ and
$$\begin{align}g(x^{12})&=x^{60}+x^{48}+x^{36}+x^{24}+x^{12}+1\\&=(x^{60}-1)+(x^{48}-1)+(x^{36}-1)+(x^{24}-1)+(x^{12}-1)+6\end{align}$$
Answer: We have $$g(x^{12}) = (x^{60} + x^{48} + x^{36} + x^{24} + x^{12} + 1 ) =   (x^5 + x^4 + x^3 + x^2 + x^1 + 1) \cdot q(x) + r(x)$$ where $r(x)$ is a polynomial with degree no greater than four.
To find $r(x)$, we can plug in the roots of $g(x)$, the non-one sixth roots of unity, into the equation. Let these roots be $\omega, \omega^2, \omega^3, \omega^4, \omega^5$. Note that for each of these, $x^{60} = x^{48} = x^{36} = x^{24} = x^{12} = 1$. Therefore, for any $i$, $r(x) - 6 = 0$ for all values of $\omega^i$.
Therefore, $r(x) - 6$ is a with five roots and degree no greater than four, and it follows that we must have $r(x) = 6$.


How long can I drive my truck with the wrong coolant in it?

Question: I put the wrong coolant in my '99 Ford Expedition and I was wondering how long I could drive it before I need to have it flushed and have the correct coolant put in?
Comment: "Green" and "orange" aren't kinds of coolants, they are colours or coolants. Some coolants are chemically compatible yet have different colours. What did you put in there? What does the container say it's formulation is? Or which brand is it?
Comment: What coolant is it supposed to take, and what did you put in?
Comment: It's supposed to take the green kind and I put in the orange
Comment: There probably isn't a real answer for this but I rain an engine with a silicate coolant for over year by accident. It specially required non silicate coolant.  I just did a very thorough flush with water and then filled with the correct stuff. The car was fine for a further few years but was scrapped for other reasons.
Answer: It really depends on the kind of coolant that the maker specifies, the kind that was in the cooling system, and the kind that you put in.
Some coolant combinations are incompatible and, if mixed, form a sludge that greatly diminishes the cooling capacity of the system. You can't run that for long at all. As in, just don't.
On the other hand, other coolant formulations are specified for corrosion protection and you can probably run the wrong stuff for a reasonable amount of time (weeks, maybe more) without problem.
The bottom line is that without knowing the specifics:

The coolant specified for your vehicle.
Original coolant type that was in the engine.
New coolant type.
How the mistake happened – putting in the wrong coolant after a through flush is a very different (smaller) problem than mixing the two when coolant was low.

It is almost impossible to give you a meaningful answer.
Answer: No problem!
Drive as much as you like and replace the coolant whenever you have enough free time.
Most of the modern coolant liquids are ethylen glycole based formula and they could be blended without making trouble.
all types of the coolant liquids are chemically stable compound and they are not going to engage in any chemical operation easily.
Comment: IAT and OAT coolants are **not** all compatible with each other and the reaction that you get when you mix them can produce a "sludge" that can clog radiator passages.
Comment: @dlu May you please provide an example for those two formula that may blend chemically ?


Do all total solar eclipses have the ring of fire when observed from ground?

Question: I was recording the phenomenon and then I soon realised that the ring of fire don't dissappear, is it because of the apparent size of the moon and sun as well as the relative distance so that every eclipses I see would alway have the ring of fire on it? Also I ruled out lensing because the moon is not massive enough right?
Comment: This should be trivial to look up.  Have you seen *any* of the photos from the last 50 or so total eclipses?
Answer: No, some solar eclipses are annular and some are total.
The difference is in the Moon's distance at that moment in its eccentric orbit around the Earth.
Hermit Eclipse has some illustrations which may be helpful.
In an annular eclipse, the Moon is farther than average and appears slightly smaller than the Sun.
Some of the solar photosphere remains exposed, briefly appearing as a ring for observers on the central path.
The phrase "ring of fire" applies to annular eclipses.
The eclipses of 2019-12-26 and 2020-06-21 are annular.
In a total eclipse, the Moon is nearer than average and appears slightly larger than the Sun.
Along the central path, the photosphere is completely obscured, briefly allowing observation of the solar corona.
There may be a "diamond ring" effect before and after totality as a bit of photosphere shines past low regions on the lunar limb.
The eclipses of 2019-07-02 and 2020-12-14 are total.
In the present few centuries, annular eclipses are slightly more frequent than total eclipses.
Answer: Yes, it's the relative size as seen from earth. With the sun blocked out by the moon we can see the corona - it is rather large but normally drowned out by the light from the photosphere.
As Carl suggested, you can easily look at photos of total eclipses - as long as the exposure is set correctly, you can always see the corona at totality.
Comment: @MikeG's answer is correct. An annular eclipse actually shows part of the sun as an "annulus" a "little ring"(latin), it happens when the moon's angular size is smaller than the sun's as seen from earth. The corona is best visible (through filters !) during a total solar eclipse (the moon covers all of the sun's surface).


How to export a map (satellite image, 3 bands) to Tiff without losing the resolution in Qgis.

Question: I manually improve the colour contrast of landsat images. The printing in pdf afterwards is OK, as it maintains the resolution due to the high dpi. Now I am interested to obtain a kmz/kml file of the satelite image for visualization in Google Earth. I have downloaded Maptiller which allows to load in tiff, and generate kmz. My problem, however, is that saving the map as tiff results in a maximum image size of 2.3MB, hence the resolution gets lost before the actual conversion to kmz. I used the garmincustommap plugin of Qgis, but same issue...Seems that the only straightforward way would be arcGis or globalmapper, which I do not have access to. Any suggestions?
Comment: kml and kmz s have a limited capacity as a standalone file. Kmz s which refer to a server resource can allow Google Earth to display extensive imagey.   You may need to consider what you are trying to achieve.
Answer: Right Clic on your raster>Save as>GTiff (try to keep Output Mode in Raw Data)


Which is the best 3D printer to print bodies scanned?

Question: I want to print people's bodies scanned (or get 'minimes', see the Figure 1). And I watched that the printer 'project 660' is very good to do this (Figure 1). But, the price of that printer is really expensive, roughly $60'000. And If you want to get a 'minime' printed by that printer, the cost is $230 for a model of 10cm. For me that price is expensive too.
Does anyone know what printer I could use in order to print 'minimes' with:

Good resolution, or details of the person's face (for a model of 10cm) and a good smooth surface of the model printed (Figure 1).
Ability to print complex models such as bodies (Figure 1) without problem.
Inexpensive: less than $150 per 'minime'.
An option to print in color.

Thanks.
Figure 1: Models printed
Comment: Hi! This question is very broad, as it has many possible answers. Almost any printer could be an answer, as you haven't included many criteria on what kind of printer you need. Questions that ask for "the best" X are not very suitable for stack exchange, because what is "the best" is very subjective. Could you maybe add some more information based on which the potential answers to this question could be narrowed down?
Comment: Hi, Francis. For the reasons pointed out by Tom, I have to put it *on hold* for now. You may vote for your question to be opened after eventual edits.
Comment: I edited the post, please let me know any problem.
Comment: What does "no expensive" mean? Under $100? Under $500? Under $1000?
Comment: Less than $150. I've just changed it
Comment: What I need to do to skip from the hold?
Comment: Hi, Kuroro! While recommendation questions generally are discouraged here on 3D Printer SE, I am willing to open your question due to your particular requirement of *"a cheap printer that can print in full color"*. In my opinion, this requirement is specific enough to eliminate most common 3D printer alternatives. Good luck! :-)
Comment: where did you get the idea that printing a 10cm "mini-me" costs 230$ ?
Comment: In this video, I saw a copy of a hand if someone knew what it was https://youtu.be/cEJHXDsYeww
Answer: I do not think there exists a printer that meets your requirements. "Cheap"/hobbyist printers roughly fall into two categories:

FDM: does not meet your requirement for sufficient detail and smooth surfaces in the face (and can not print in color).
SLA: meets your requirement for detail in the face but can not print in color. If you are willing to drop the color requirement, this would be a good choice.

There are some hobbyist projects to do full color printing, but they are in a rather early stage. One option is colorpod that can be used to convert an FDM printer (such as the Ultimaker, but the principle works with any printer) however it is in a rather early stage of development and not very reliable yet. Another option is Plan B but that is a DIY project and not available for purchase (and is not very mature either).
That leaves you with the commercial color options. You've already ruled out the 3D systems/projet machines. Another (slightly cheaper) commercial option is MCOR IRIS but it also runs in the tens of thousands. While researching this question I stumbled upon 3D Pandoras but it seems a relatively new company so it may turn out to be a literal Pandora's box (they mention "most affordable filaments" as one of the advantages of their printer even though it doesn't use filament at all) - and prices are not listed on their website.
Comment: Good FDM gives better result than bad SLA and still costs 10 times less.
Comment: Anyone Knows -Mcor ARKe?. It uses paper ... but, is the quality really good for 'minimes'?
Comment: @Kuroro You can see some sample pictures on the [product page](http://mcortechnologies.com/3d-printers/arke-3d-photorealistic-colour-printer/). They don't look bad, but the 3D systems/project/ZCorp machines do a better job.
Comment: Hi Tom van der Zanden.
Is MCOR really bad?, because you wrote: "runs in the tens of thousands". Could you explain me a little more?.
Answer: There are several options for printers that can produce high-quality 'minimes' at a lower cost. One option is the Formlabs Form 3, which has a maximum build volume of 14.5 x 14.5 x 18.5 cm and can print in color. Another option is the Prusa i3 MK3S, which has a build volume of 25 x 21 x 20 cm and can also print in color. Both of these printers have good resolution and can handle complex models. Another option is the Creality CR-10, which has a larger build volume of 30 x 30 x 40 cm and can print in color. However, it may have a slightly lower resolution compared to the other two options. These printers range in price from \$500 to \$1000, making them more affordable than the 'project 660'.


How do you solve a 2nd order differential equation of the form $v = v' - v'' +C^t +D^{t+E}$

Question: I've been working on an economic simulator for a game I've been making and in order to simulate the velocity of money, I created the differential equation of the form $v = v' -v'' + C^t + D^{t+E}$. However, after creating it, I realized that I didn't actually know how to solve it (the most advanced course in mathematics I have taken is Calculus BC), and neither Wolfram Alpha nor Sage seem to be able to use a method to either solve or approximate the solution. Thanks for any help in advance!
Comment: can you say something about the variables?
Comment: i think you can only plot a solution if you have values for the parameters and the constants
Comment: WolframAlpha [solves this](http://goo.gl/SDs2DQ) without difficulty. The open source program Maxima also solves it without difficulty. Sage tries to call Maxima but chokes due to the poor interface. There are many purely numerical solvers that can deal with the equation as well.
Answer: Try a solution
$$v = aC^t + b D^{t+E}$$
where $a,b$ are constants. The motivation for this is that if $v_1,v_2$ solves
$$v_1 = v_1'-v_1'' + C^t$$
$$v_2 = v_2'-v_2'' + D^{t+E}$$
then $v = v_1 + v_2$ solves the equation
$$v = v'-v'' + C^t + D^{t+E}$$
plus the fact that for any constant $Y$ we have $(Y^t)' = \log Y \cdot Y^t$. Plugging our guess above into the equation gives us
$$C^t(1 + \ldots) + D^{t+e}(1+\ldots) = 0$$
where $1+\ldots$ will be some constants. In order for this to hold for all $t$ we need both $1+\ldots = 0$. This gives you two equations for $a,b$ and the particular solution.
In order to get the most general solution note that for any $v_3$ that solves
$$v_3 = v_3' - v_3''$$
then $v= v_1 + v_2 + v_3$ will also be a solution to your equation.
I leave solving this to you (this is a homogeneous linear ODE and can be solved with the standard method of trying $v_3 = e^{\lambda t}$ and solving a quadratic equation for $\lambda$ to give you the two solutions, see for example this page for an explanation). If you do it correctly (and if I have done it correctly) you will get
$$v = \frac{C^t}{1 - \log C + \log^2 C} + \frac{D^{E+t}}{1 -  \log D  + \log^2D} + Fe^{t/2}\cos(\sqrt{3}t/2) + Ge^{t/2}\sin(\sqrt{3}t/2)$$
where $F,G$ are free constants determined by the initial conditions. For example if you want to set the initial conditions at $t=0$ you plug in $t=0$ above to get:
$$v(0) = \frac{1}{1 - \log C + \log^2 C} + \frac{D^{E}}{1 -  \log D  + \log^2D} + F$$
This fixes $F$ in terms of $v(0)$. Taking the derivative of $v$ and plugging in $t=0$ gives:
$$v'(0) = \frac{\log C}{1 - \log C + \log^2 C} + \frac{D^{E}\log D}{1 -  \log D  + \log^2D} + \frac{F}{2} + \frac{G\sqrt{3}}{2}$$
which fixes $G$ in term of $v'(0)$.


Is mattermost encryption for group messaging and file transfer secure?

Question: Mattermost is an open source group messaging and file transfer service, designed as an alternative to Slack. Their account of their security setup is detailed here. Are the encryption options it offers for the group messaging and file transfer services it offers secure, if it's set up on a secure, internal server?
Answer: After reading the security details it seems very secure for me. Just to remark some details:

Using AES-256 Algorithm: AES (Advanced Encryption Standard) is the Standard and most widely used private key algorithm.
RSA with 2048 bit is the most widely used public key algorithm in data transmissions.
TLS: is a high security transmission protocol used widely too.

Logging, History, Updates... also makes mattermost so secure.
Answer: Messages are encrypted while transmitting between the clients and server, but are not encrypted at rest (in the database). This means anyone with database access can read both channel and private messages.
Not encrypting them, among other things, allows searching.
Encrypting the data storage is left up to the underlying operating system:

Encryption-at-rest is available through hardware and software disk encryption solutions applied to the Mattermost database, which can reside on its own server within your infrastructure.

These can include full disk encryption, but a sysadmin with sufficient access to the server can always get around that.


Typos have been authorized

Question: What is the meaning and use of above sentence if somebody replied through their mobile device and wrote below sentence in the lower part of email

Sent from my mobile device. Typos have been authorized.

What is his/her intended meaning here?
Answer: I believe the writer is basically saying:

I typed this from a mobile device. Therefore, I didn't have access to a full keyboard, or a spell-checker. Instead, I typed it on a small screen using only my thumbs, so don't be surprised if you find a typo.

It's meant to be a humorous and concise way to alert the reader that there may be typos.
My guess is that the writer spends more time proofreading emails sent from a desktop or laptop computer than when using a cell phone to respond to emails, or that the person isn't an experienced texter, and has noticed that they are more prone to make typos  when sending a text message. Rather than being embarrassed or frustrated by these typos, or spending a lot of time correcting them, this line gets appended to their messages instead.
I would guess that the writer has this as part of a regular "signature" in their mobile device, and that it shows up at the end of many if not all of the messages sent from their phone.
Usually, authorization comes from a higher authority, like a boss, or a corporate decision. In this case, the person is "authorizing" typos because he or she has made the conscientious decision to not worry about them if they happen, as if to say, "What do you expect? I'm typing this on a tiny screen, for crying out loud!"
I found it clever and I literally LOL'ed when I read your question.
Answer: "Typos have been authorized" is not common or well-known, and as far as I know it has no single, well-understood meaning.  Thus, to find out the sender's intended meaning of the phrase, you will need to ask him or her.  What we can address here are possible meanings.
(a) One of the simplest interpretations: "I take responsibility for any typos in this message".  That is, the sender acknowledges the message may contain typos, and (probably for the sake of expediency) is not going to root them all out.
(b) A variant of the above: "There may be typos in this message.  I don't care".   Again, the sender acknowledges the message may contain typos, but because it is so tedious to fix them using the mobile device, will do nothing about them.
(c) The sender had another person glance at the message (or had a spell-check or grammar check program test it) and the person or program approved sending the message as is.  In this interpretation, authorized is used with its dictionary meaning,  "Explicitly allowed", and the agent who has allowed the typos is another person or a program, vs the sender, who did the allowing in the other two interpretations.

Typos have been authorized


Why can't I create contracts using example code?

Question: I am a noob when it comes to creating contracts. Every contract I try to deploy using the example code for new coin creation seems to have failed even though I paid for it, what am I doing wrong? Did I run out of "gas", if so how do I pay enough for it?
Answer: Yes, you did run out of gas. There are two steps you need to complete to ensure that the contract has enough gas.
1) Ensure that  you should have enough Ether in your wallet to be able to fund this transaction. If you are on a test net, you should be able to mine for Ether.
2) Also, check that the  Maximum Gas provided is more than the estimated gas.
Comment: I tried deploying the contract with the fee slider set to maximum and it still failed. I paid 0.0928 ether fee, gas used 400,000 and gas price at 0.232 ether per million gas. What did I do wrong this time?
Comment: You will need to increase the maximum gas provided in the next screen. Unfortunately, the slider does not work too well. Have a look at this conversation which discusses  how to increase the maximum fee provided. https://ethereum.stackexchange.com/questions/15249/very-strange-glitch-in-mist-provide-maximum-fee-estimated-fee-consumption/15250?noredirect=1#comment16037_15250


Resize a rebuild CPQ hardware RAID

Question: I have a HP/Compaq DL360 with two 73gig HDs and a Smart Array 6i in a mirror, and CentOS 5.5.I'm low on space, so I alternately swapped in two 300 gig units and let the RAID card rebuild them. Now I have two 300's that the HP Linux CLI utility sees, but I can't resize the partitions with a Gparted Live CD. I tried to add new partitions with fdisk, but it does not see any of the new free disk space. Do I have to add the space in the RAID BIOS setup?
Answer: You have to extend the logical drive within the Array Configuration Utility. In the hpacucli utility, you run ctrl all show config detail, take note of the unused space. See this example where I have 432GB of raw space, but only a portion of it allocated to logical drives:
Smart Array P410i in Slot 0 (Embedded)    (sn: 5001438006FD9A50)

   array A (SAS, Unused Space: 265022 MB)

      logicaldrive 1 (72.0 GB, RAID 1+0, OK)
      logicaldrive 2 (72.0 GB, RAID 1+0, OK)

      physicaldrive 1I:1:1 (port 1I:box 1:bay 1, SAS, 146 GB, OK)
      physicaldrive 1I:1:2 (port 1I:box 1:bay 2, SAS, 146 GB, OK)
      physicaldrive 1I:1:3 (port 1I:box 1:bay 3, SAS, 146 GB, OK)
      physicaldrive 1I:1:4 (port 1I:box 1:bay 4, SAS, 146 GB, OK)

Do you have the graphical cpqacuxe utility installed? You can do this via the graphical interface as well... But either way, the point is to expand the logical drive to the new array size (reflected by the new 300GB disks). From there, you'll have to reboot. At that point, the usual partition utilities (fdisk, parted, etc.) will see the space.
Also check this link for another example: http://www.flagword.net/2010/12/expanding-sb40c-with-hpacucli/
Or the Configuring Arrays on HP Smart Array Controllers Reference Guide.

Resize a rebuild CPQ hardware RAID


Powering a number of Pi from a single bench top power supply

Question: I'm thinking of investigating the Bitscope Blade QUATTRO to host up to forty boards. Looking at the details each Blade can power the boards off a single supply, which need not be at 5V with up to 3A (4A surge) power budget. Will this support a fully connected Ethernet cluster with a 2.5 250G disk per pi and sensor inputs to one Pi per blade.
Comment: Tell us more about your requirements and tradeoffs considered. My initial thought was that a single 12V LED driver can supply ample current to a lot of DC-to-DC buck converters off a single wall outlet.
Comment: From Bitscope Blade's site "Reliable power suppy has been an ongoing issue for Raspberry Pi and many other USB powered embedded computers.

It's a deficiency in the USB specification more than anything else.

It gets even worse when you try to power many downstream USB devices from one Raspberry Pi, let alone when you try to do the same thing with multiple Raspberry Pi.

BitScope Blade solves these problems by powering Raspberry Pi via the J8 socket (instead of the micro USB socket). "

So I'm looking to have 10 Quatro cards (40Pis) each with a 250G HD networked as a Flink cluster.
Comment: Thanks for the feedback. I've sketched out an initial answer that we'll edit as needed.
Comment: Sorry, but shopping requests of the form, "Which whatsit should I buy?" are explicity [off-topic](http://raspberrypi.stackexchange.com/help/on-topic).
Comment: Interesting bit of kit! - but I'm not sure that you can get around the shopping request aspect - unless you rephrase it to ask **how** can I power this *monster*? 8-P
Comment: Powering multiple Pi's is actually a common problem with non-obvious solutions.
Answer: This answer assumes you already understand Raspberry Pi power limitations.
Powering many Raspberry Pi's is a challenge in that they need to be properly supported and cooled. Applying 5V directly via the expansion header pins 2&4 is often more mechanically stable and electrically reliable than using the USB power. This consideration naturally leads to the use of a separate board (i.e., blade) to which the Pi is mounted via the expansion header.
A blade provides mechanical support for multiple Raspberry Pi's attached via their expansion headers. The blade will often have its very own voltage regulator for supplying the attached Pi's. The blade power supply will usually be a DC-to-DC switching regulator or buck converter (search SE Electronics), that accepts a range of DC voltages (e.g., 7-48V) provided by a master power supply.
To determine the needed master power supply for Pi blades, you will need to measure the power requirements of a single fully loaded blade with all expected peripherals attached and running actual software. If possible, include cooling as well for accurate measurement. This measurement is easily done with an inline meter. Knowing the wattage required will help you size and purchase the required master power supply for your entire application.
Although bench power supplies can serve as a master power supply, it may be more cost effective to consider dedicated power supplies such as LED drivers, which are designed to supply power cheaply and reliably over a long time. If power outage is a concern, then a battery or UPS can provide needed protection from power failure. You can even choose solar + 12V battery, etc. In other words, your own requirements will best guide your search.
Answer: The Quattro has its own integral switching power supply to generate the 5v supply to the Pi computers. The current rating of the external supply for each quattro board  will depend on the voltage you provide. At 9v it will need 4A; at 48V it will need just 500 mA.
You might want to consider using a UPS if you want to ensure a safe shutdown of all the Pis in the event of mains failure.


Distributed FS with deterministic multiple masters?

Question: I'm looking for a distributed file (or other storage) system for managing a very large number of mutable documents. Each document can be rather large (1-100MB). Some reads need to be guaranteed to be working from the latest data, and some can be read from eventually-consistent replicated data. Each document could be a self-contained file (say, a SQLite database or other custom file format).
For optimal performance, the node of the distributed file system on which writes happen for each document must be different. In other words, server A is the master for document 1 and server B is replicating it, but server B is the master for document 2 and server A is replicating it. For my application, a single server is not going to be able to handle all of the write traffic for the whole system, so having a single master for all data is not acceptable.
Each document should be replicated across some number of servers (say, 3). So if I have 1000 documents and 10 servers, each server would have a copy of 300 documents, and be the master for 100 of those. Ideally, the cluster would automatically promote servers to be masters for documents whose master server had crashed, and re-balance the storage load as new servers are added to the cluster.
I realize this is a pretty tall order... is there something available that meets most of my core needs?
Answer: I think HDFS would fit the criteria you listed above.


Java 8, Update 73 not installing

Question: I'm following the procedure on Oracle's website to install Java 8, update 73. When I get to step 5 in the procedure and click "Next," the installer window quietly shuts down without and without an error message and Java never installs. I have tried disabling SIP to no avail.
Answer: Uninstalling existing JRE per these instructions and installing the latest Java Development Kit from here did the trick.

Java 8, Update 73 not installing


Using MySQL ver. 5.5.55 in a production env

Question: Is it still OK to use this older version of MySQL on a production web server (LAMP on Ubuntu 14.04)? It's a low traffic volume business website. Loads fast enough. So far, no serious issues (like being hacked or something).
Also we use older version of PhpMyAdmin (ver. 4.0), so my question also regarding this too.
Answer: There are four reasons to upgrade the software:

Significant bug was removed
Security breach was removed
Hardware have
to be changed
Database structure was modified dramatically and
require some features not available in the older versions.

Updates performed just for software actuality are inappropriate in the production.
phpMyAdmin is well-known as unsecure software with lot of breaches so its location should be at least password-protected and restricted to the secure subnet(s).
Comment: As far as I know, MySQL 5.5 hasn't reached its EOL (like what happened to PHP 5.5 recently). That's why I keep using MySQL 5.5 I'm not aware of any serious issues with it and neither our hardware nor db structure require any changes. So I guess there's no need to upgrade MySQL for now...
Comment: Even when EOL will be reached if it fits your needs and secure. Unfortunately, phpMyAdmin increases the risks alot.
Comment: We have Web Application Firewall enabled and also the URL for phpMyAdmin is different (not mysite.com/phpmyadmin). Also there's fail2ban server and, of course, HTTPS.


Can Wayland have network transparency implemented as a plugin?

Question: To my understanding there's no reason why a Wayland plugin can't hide the app in the local machine, forward it's windows to a remote machine, and feed the app input from the remote machine. Am I wrong?
Answer: What a lot of people don't understand about about Wayland is that it's not intended as a complete replacement for everything Xorg does, if it were then it would have no advantage over Xorg. We've become so accustom to the display server protocal, X11, supporting network transparency, font rendering (hardly ever used anymore), drawing of polygons and archs (also hardly ever used anymore)... that we simply expect that that's what a display server does.
Wayland is a display server, and only a display server. It composites buffers to the screen using a very basic protocol, and leaves all other features to a different level, they are out of the scope of Wayland.
One way to think of it is to ask a similar question about the sound architecture in Linux rather than the graphics architecture.
Does ALSA support network transparency? The answer is no, that's outside the scope of ALSA. But you can still use network transparency in linux, that's why we have pulseaudio.
Your question is slightly different, but I think is still based on the idea that this is something Wayland itself should support.
Can ALSA have network transparency implemented as a plugin? I would answer no, because I wouldn't consider pulseaudio to be a "plugin" for ALSA, but rather something that runs on top of ALSA.
So "Can Wayland have network transparency implemented as a plugin"? No, but that doesn't in any way mean that you won't be able to use network transparency with Wayland.
Xorg can run on top of Wayland, and just as efficiently as if Xorg itself were the display server. So you can still use "ssh -X" and get a local window for a remote app, running right alongside all your other local windows that may be native Wayland clients.
So Wayland will in no way prevent you from using X11 applications remotely, exactly as you do today. And in addition it allows efficient implementations of other protocols for network transparency, like RDP, VNC, and even HTML5: http://blogs.gnome.org/alexl/2010/11/23/gtk3-vs-html5/
I hope that short novel answers your question :)
Comment: It does not answer my question. I already know of X11 being implemented as a Wayland client, which is why I asked specifically about the ability of Wayland's plugin mechanism. So what I want to know is: can Wayland's compositor plugins implement network transparency, even if it's in a somewhat hackish way, so that apps that are written directly to Wayland without an intermediary layer like X11 still get network transparency.
Answer:
So what I want to know is: can Wayland's compositor plugins implement
  network transparency, even if it's in a somewhat hackish way, so that
  apps that are written directly to Wayland without an intermediary
  layer like X11 still get network transparency.

Yes, a Wayland compositor could do this. I don't expect there to be many applications interfacing directly with Wayland rather than through toolkits like Qt/GTK though.
Answer: Switching terminology from Wayland, which now is the name just for the protocol, to Weston, the reference Wayland protocol implementation.
So the answer is: yes, Weston has a module that implements network transparency without passing through X11. See for example this RealVNC Wayland implementation.


Object being distorted when fixing lighting

Question:

So I have a problem with some unwanted wierd lighting on my model, which I would like to remove. But when i go to edit mode and use Ctrl+N to fix it. Then when i change mode to sculpt or object mode it comes out distorted like this. Any ideas how to fix this problem?
Comment: Welcome to Blender.SE! To make your images available for previev for others, please either share the images in your dropbox profile or even better upload them right here using *Image* button (or `Ctrl`+`G` while in the Ask Question field).
Comment: I did not know how to upload the pictures. Thank you!
Answer: When dealing with sculpting it's very important to check whether your model doesn't have any flipped normals before adding Multires modifier (if you flip them after subdivided and sculpted, recalculating shouldn't make any problems. But making any changes in Edit mode on the sculpted model anyway will make you some distortions). You still can recalculate them at any time, but that will result in a mess you see in your case (or even worse).
There are several ways possible taking into account that sculpting must be saved:
Smoothing faces with flipped normals

Enter Edit mode of the corrupted object, select faces with flipped normals and assign them to temporar Vertex Group.
Add Smooth modifier to this object, set created vertex group in the Vertex Group option of the modifier to make it influence only on it.
Set the Repeat value to something high, like 30 or 50, so to make messy vertices return to their place.
Recalculate flipped normals using Ctrl+N.

The Smooth modifier will let you make those faces / vertices stop being distorted and moved far away, at the same time the original sculpting in other areas will be preserved.

This way has disadvantages, of course:

if there are a lot of faces with flipped normals it won't really help you - nearly all faces will be added to group smoothed by the Smooth modifier and that will be the same as just using Smooth brush in Sculpt mode or recreating from scratch all the sculpt.

Leaving inverted normals
It's pretty straightforward - the inverted normals are left as they are, and you continue sculpting, including them if needed. You'll need to recalculate normals after applying Multires modifier (and probably make some adjustments even then).
The trick here will be that as the normals are flipped, the brushes will behave in the opposite way, so on these faces you'll need to use Subtract mode of any brush.

The disadvantages:

It may be quite complex to create any smooth transitions on the areas where flipped / unflipped faces meet as brush may act somewhat unpredictably.

Smoothing in Sculpt mode
It should be possible to see messed vertices while in Sculpt mode (but I managed once to see them only while in Object mode), and it's possible to smooth them using Smooth brush (press S while in Sculpt mode). Probably it won't be easy to smoothen with brush exactly tjose distorted areas, but it may be worth trying if there isn't big amount of them.

So it's a lot easier to check that there aren't any flipped normals in the model before you add sculpting then to deal with repairing that after and trying to preserve hours of sculpting work.
Comment: Thank you! I'll try it out, but it may be difficult. In the worst case scenario i'll just have to make it over again i guess.
Again, thank you very much!


Dump md5 and sha1 checksums with a single command!

Question: I am looking for command or utilities for calculating md5,sha1 hash value by one command.
Right now ubuntu has sha1sum and md5sum command for calculating hash value.
Comment: Why do you want it? Usually you want to be able to verify hashes after generating them. For example, to generate a hash: `md5sum hosts`. Then, to verify this result: `echo "b9adfb2e2022a3a84ba06b55eeb2dc64  hosts" | md5sum --check` (should give: `hosts: OK`)
Comment: suppose if want to calculate 'hash value' of 500 GB hard drive ie both sha1 and md5. if i calculate one by one (using sha1sum and md5sum) would take double time. but if could be done with single utilities same as windows software then would be my desired answer.
Answer: You can achieve this with some proper bash ninja-fu. :)
You know the procedure to calculate one at a time:
$ echo abc | md5sum
0bee89b07a248e27c83fc3d5951213c1  -
$ echo abc | sha1sum
03cfd743661f07975fa2f1220c5194cbaff48451  -

Edit: as @gertvdijk suggested, and reading the info pages a bit more, this can be done directly with tee and Process Substitution supported by modern shells, without redirects. This way you can pass your data to two processes and one file using tee:
$ echo abc | tee >(md5sum) >(sha1sum) > output.txt

It's also possible to chain if you need more, but you have to take care of STDOUT from all the subprocesses. This will NOT give you the expected result, but mixes the first two checksums together with the data in output.txt:
$ echo abc | tee >(md5sum) >(sha1sum) | tee >(sha256sum) >(sha512sum) > output.txt

If you redirect the checksums to a file inside the substituted processes, you can chain these as you like:
$ echo abc | tee >(md5sum > /tmp/md5.txt) >(sha1sum > /tmp/sha1.txt) | tee >(sha256sum > /tmp/sha256.txt) >(sha512sum > /tmp/sha512.txt) > output.txt

Here's my initial suggestion without process substitution, but which allows chaining/recursive use without mixing the data and the output:
$ echo abc | tee -a /proc/self/fd/2 2> >(sha1sum) > >(md5sum)
0bee89b07a248e27c83fc3d5951213c1  -
03cfd743661f07975fa2f1220c5194cbaff48451  -

The trick here is to use tee, which duplicates the data to STDOUT and a file. We're being clever by telling it to write the data to the file /proc/self/fd/2, which happens to always be the current process' STDERR file descriptor. And with the > >(program) syntax we can redirect each file descriptor to a program's STDIN instead of a file. Just like |, but with more control. > >(md5sum) redirects STDOUT to the md5sum program, while 2> >(sha1sum) redirects STDERR to the sha1sum program.
Note that the order of 2> and > seems to matter, I have to put 2> first on the command line. These are evaluated from right to left, but I'm not sure why this makes a difference.
To do this on a file or a hard drive, you should replace "echo abc" with a cat or a dd, eg:
dd if=/dev/sda bs=8k | tee -a /proc/self/fd/2 2> >(sha1sum) > >(md5sum)

The nifty thing about this is that you can actually recurse and run several at the same time, not just two. The syntax gets hairy, but this works:
echo abc | tee -a /proc/self/fd/2 2> >(tee -a /proc/self/fd/2 2> >(sha256sum) > >(sha384sum) ) > >(sha512sum)

If you want to capture the result and use it in a script, that works too:
A=$(echo abc | tee -a /proc/self/fd/2 2> >(sha1sum) > >(md5sum))

Now $A is a string containing all the output, including newlines. You can parse the values out later too:
echo "checksum=[$(echo "$A" | head -1 | cut -d " " -f 1)]"

I'm not sure you have any guarantees regarding ordering of the output though.
Comment: +1. `tee` and clever use of output redirection in the shell is the way to go. This saves a lot of resources, especially when reading large files.
Comment: By the way, I think you don't need to redirect to stderr to duplicate the output of the stream. The use of a subshell will also do the trick, maintaining stderr. See my example here in a [blog post](https://blog.g3rt.nl/luks-smartcard-or-token.html#enhance-security-avoid-temporary-key-storage).
Comment: @gertvdijk Right, process substitution is cleaner, and easier to chain (you don't need to recurse). I'll update my response.
Comment: Nice. I'd give you another upvote if I could. :-)
Comment: While these work well for nice small files, you're doubling the efforts and processing time for larger files which I'm looking to avoid...
Comment: @EkriirkE, what do you mean by doubling the efforts? Yes, the data is duplicated for each checksum, but this is still only done in one pass. You could optimize this a bit more by writing a single application that does everything, and I'm sure there are tools that do this already, but for large amounts of data the IO tends to be the bottleneck. The above works great for huge files or disk images. Have you tried timing this vs just reading the data?
Answer: Cant help you with command line but I know a GUI tool named as quickhash.
You can download that tool from Quickhash
Description:

A Linux and Windows GUI to enable the rapid selection and subsequent
  hashing of files (individually or recursively throughout a folder
  structure) text and (on Linux) disks. Designed for Linux, but also
  available for Windows. MD5, SHA1, SHA256, SHA512 available. Output
  copied to clipboard or saved as CSV\HTML file.
Answer: Here i have find one python script from source which calculate hash values. and also i find some statistics about hash value calculation.

 - `md5sum` takes 00:3:00 min to calculate 4GB USB.
 - `sha2sum` takes 00:3:01 min to calculate 4GB USB.
 - While phython script takes 3:16 min to calculate both MD5 and SHA1.

//Script start from here
def get_custom_checksum(input_file_name):
    from datetime import datetime
    starttime = datetime.now()
    # START: Actual checksum calculation
    from hashlib import md5, sha1, sha224, sha384, sha256, sha512
    #chunk_size = 1 # 1 byte -- NOT RECOMENDED -- USE AT LEAST 1KB. When 1KB takes 1 min to run, 1B takes 19 minutes to run
    #chunk_size = 1024 # 1 KB
    chunk_size = 1048576 # 1024 B * 1024 B = 1048576 B = 1 MB
    file_md5_checksum = md5()
    file_sha1_checksum = sha1()

    try:
        with open(input_file_name, "rb") as f:
            byte = f.read(chunk_size)
            previous_byte = byte
            byte_size = len(byte)
            file_read_iterations = 1
            while byte:
                file_md5_checksum.update(byte)
                file_sha1_checksum.update(byte)
                previous_byte = byte
                byte = f.read(chunk_size)
                byte_size += len(byte)
                file_read_iterations += 1
    except IOError:
        print ('File could not be opened: %s' % (input_file_name))
        #exit()
        return
    except:
        raise
    # END: Actual checksum calculation
    # For storage purposes, 1024 bytes = 1 kilobyte
    # For data transfer purposes, 1000 bits = 1 kilobit
    kilo_byte_size = byte_size/1024
    mega_byte_size = kilo_byte_size/1024
    giga_byte_size = mega_byte_size/1024
    bit_size = byte_size*8
    kilo_bit_size = bit_size/1000
    mega_bit_size = kilo_bit_size/1000
    giga_bit_size = mega_bit_size/1000
    last_chunk_size = len(previous_byte)
    stoptime = datetime.now()
    processtime = stoptime-starttime
    custom_checksum_profile = {
        'starttime': starttime,
        'byte_size': byte_size,
        'kilo_byte_size': kilo_byte_size,
        'mega_byte_size': mega_byte_size,
        'giga_byte_size': giga_byte_size,
        'bit_size': bit_size,
        'kilo_bit_size': kilo_bit_size,
        'mega_bit_size': mega_bit_size,
        'giga_bit_size': giga_bit_size,
        'file_read_iterations': file_read_iterations,
        'last_chunk_size': last_chunk_size,
        'md5_checksum': file_md5_checksum.hexdigest(),
        'sha1_checksum': file_sha1_checksum.hexdigest(),
        'stoptime': stoptime,
        'processtime': processtime,
        }
    return custom_checksum_profile

def print_custom_checksum(input_file_name):
    custom_checksum_profile = get_custom_checksum(input_file_name)
    try:
        print 'Start Time ::', custom_checksum_profile['starttime']

custom_checksum_profile['file_read_iterations'])
    #        print ('Last Chunk (bytes)    :', custom_checksum_profile['last_chunk_size'])
            print 'MD5 ::', custom_checksum_profile['md5_checksum']
            print 'SHA1 ::', custom_checksum_profile['sha1_checksum']
            print 'Stop Time ::', custom_checksum_profile['stoptime']
            print 'Processing Time ::', custom_checksum_profile['processtime']
        except TypeError: #  'NoneType' object is not subscriptable --- basically this should happen when the input file could not be opened
            #raise
            pass
        # csv output
import argparse
script_version='0.0.2'
parser = argparse.ArgumentParser(description='Determine and print various checksums of an input file and its size. Supported checksums are MD5, SHA1, SHA224, SHA256, SHA384, and SHA512.', version=script_version)
parser.add_argument('-f', '--file', metavar='in-file', action='store', dest='file_name', type=str, required=True, help='Name of file for which the checksum needs to be calculated')
args = parser.parse_args()
print 'Processing File ::', args.file_name
print_custom_checksum(args.file_name)

Answer: You don't need "bashisms" (aka process substitution) or in the case you don't have bash but only coreutils GNU tools, you can do it with tee and named pipes.
All in one line:
$ mkfifo sha256; sha256sum sha256 & pv ~/bigfile | tee sha256 | md5sum; rm sha256
[1] 7321
15,5GiB 0:02:57 [89,3MiB/s] [===========================================>] 100%
02483696f9e698e1cc573bd0154a43e6  -
$ 9a5f63266b2bf13cb09953cd000837dd2b66ce8e5e2945369927b5ec4e324f42  sha256

Note that I am using pv here to display the progress meter (it was a big file: 15.5GB), but a simple cat would work.
Separate steps:

Create the fifo
Run one of the checksums on the fifo
On another shell 'cat' (or 'pv') the file 'tee-ing' it both to the fifo and to the other checksum
remove the fifo

You can compute how many checksums you like just by adding more fifos and tees. Unlike @ketil answer, it is "regular", you do not need to do something different each second checksum, just stack them!
You can make it simpler with pee (see here), but this utility is in moreutils that probably does not come pre-installed on your distribution unlike coreutils.
If you want results in a file instead of on the screen just add redirections like that, and it stays "regular" with many checksums
mkfifo sha256; rm -f sums.txt; sha256sum sha256 >>sums.txt & pv ~/bigfile | tee sha256 | md5sum >>sums.txt; rm sha256


How to evaluate $\int{\sqrt{\tan(x)}\,dx}$

Question: This might be a simple question, but how do you evaluate $\int{\sqrt{\tan(x)}\,dx}$ ? I've tried substitution with $u=\tan(x)$, that introduced a $\sec^2(x)$, I've also tried integration by parts, still stuck...
Comment: http://2000clicks.com/mathhelp/CalculusIntegralTableOfIntegralsSqrtTan.aspx
Answer: Take $u=\sqrt{\tan(x)}$ so that $\sec^2 x = \tan^2 x + 1 = (u^2)^2 + 1 = u^4 + 1$. hence :
$$(u^4 + 1) \, dx = 2u \, du $$
Thus:
$$dx = \frac{2u \, du}{u^4 + 1}$$
By substitution in the first integral:
$$\int (\tan x)^{1/2} \, dx =\int u \frac{2u \, du}{1 + u^4} =\int \frac{2u^2 \, du}{u^4 + 1}$$
And everything now is a matter of rational function integration, and can be solved using partial fractions. A s a hint for the next steps the denominator can be factored as $(u^2 - \sqrt{2} u + 1)(u^2 + \sqrt{2}u + 1)$
Answer: First attempt: let $u^2=\tan x$.  This gives the integral
$$I=\int \frac{2u^2}{u^4+1}\,du$$
which can be integrated by factorising the denominator and using partial fractions.  However the factorisation involves surds and is rather messy.
Better: let $u^2=2\tan x$.  This gives
$$I=\frac1{\sqrt2}\int \frac{4u^2}{u^4+4}\,du
   =\frac1{\sqrt2}\int \frac{u}{u^2-2u+2}-\frac{u}{u^2+2u+2}\,du\ .$$
Observe that except for the constant out the front, no surds are involved.  Now substitute $v=u-1$ for the first bit and $v=u+1$ for the second bit.  You will need to be careful with the algebra, but it's not all that bad.
Comment: You can factorise any polynomial $u^n+a$ by finding the (complex) $n$th roots of $-a$.  For $n=4$ there is, alternatively, a nice trick:$$u^4+4=(u^2+2)^2-(2u)^2=(u^2-2u+2)(u^2+2u+2)\ .$$
Comment: Your second method is great, but I wouldn't have known to rewrite the integral $\int{\frac{4u^2}{u^4+4}}du$ as what you did there. I think maybe this requires ingenuity... I just don't know how to come up with these...


What to do about rotten sheathing behind deck ledger

Question: My deck and patio door were improperly flashed. I've discovered that the osb sheathing between the ledger and the rim joist is rotten. Assuming the rim joist is still sound (I've not yet confirmed this to be the case), it's it all right to have a space between the ledger and the rim joist? Does that put to much tension on the upper ledger boards? Should I drive home sort of plywood spacers to fill some of the space the sheathing used to occupy?
Answer: Similar situation here. Why not just cut a clean line and add new OSB instead of leaving the dry rot and gap? There should be some building wrap, tar paper, of flashing there too.
I'm no finish carpenter but I did patch up the rotted OSB and cover it with tar paper. Now I need to add a new ledger board and flashing for the new deck.


What is the grammar behind 見よ?

Question: I just started reading a Japanese version of the New Testament when I encountered this.  The English has it as "Behold", but 見よ doesn't seem to be a command form that I am familiar with.  Is this something specific to 見る?
Answer: 見よ is an older command conjugation of 見る (see http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1239056022 if you can read it).
Basically, [見]{み} is  the masu stem of 見る -- used 見ます and 見ない. Drop the part after the stem and adding よ makes it a type of command.
見ろ is of course also a type of command.

What is the grammar behind 見よ?


What versions of Windows ship with ICACLS

Question: Can someone point me to a list somewhere that states which versions of Windows (client and server) ship with ICACLS?  I need to know going back to approximately the Windows XP era, and unfortunately don't have access to baseline images (someone may have manually put ICACLS on the machine if it did not have it).
Comment: I just did a google search **Icacls is a command-line utility that can be used to modify NTFS file system permissions in Windows Server 2003 SP2, Windows Server 2008, Windows Vista ...** and of course **icacls.exe (included in Windows Server 2003 SP2 and later)**
Comment: Does Windows XP ship it? I am assuming not since it predates Server 2003.  Also, does a baseline Server 2003 install (non sp2) not include it?
Comment: I have no idea. I found that information based on a Google search. I would assume the utility was there by default or easily installed through Windows Features.
Answer: No, ICACLS is not available in Windows XP.
ICACLS ships starting from Windows Server 2003, i.e., from Windows Vista era onwards.
For previous versions of Windows such as XP, use CACLS instead.


Windows 10 modern-ui apps wrong language

Question: I've installed Windows 10 official release (not the preview) from Windows 7 Ultimate SP1 and I've some problems with the language.
My OS is in French but all my modern-ui apps (weather, store, calendar,...) are in English. I've W10 Professional and I precise that when I had W7, I had to set default language to French after the installation (this was an english version of Windows).
Have you some ideas ?
Answer: I've solved my problem by putting in the languages settings the French language at the top. After some restarts all my modern ui apps are in French.
Comment: It looks like orders matters (i.e. first language not supported by application, take second, if not supported take third...)
Comment: Very helpful answer.  Who would have guessed that a presented Languages choice of English (Canada) would be invalid?  My Windows 10 Pro (Version: 1607, OS Build: 14393.351) Modern Apps defaulted to the next language on the list, so had to make that English (United States) to get an english "skin" for the Modern Apps.
Answer: Registered just to post this, hope it helps others who got fustrated with it as well.
Under Control Panel > Language > Advanced Settings > Override for Windows display language
Defaults follows your language setup, you can choose to select what language you wan't to show here.
Answer: It's a late answer, but when I had the same problem I solved it very quickly and easily.
I live in Germany and love my OS to be in English. In order to achieve a full English OS, including apps, and a German keyboard layout I went into my locale settings (Settings => Time & Language => Region & Language) and first off moved English (which was set to override the OS language) to the top. Then I clicked on English, clicked on Options and directly clicked on Add a keyboard and selected the German keyboard layout. After that was set I removed the US keyboard layout and then had Windows 10 displaying in English, including all of the apps, with a German keyboard layout.
I hope this answer alone might help or would give you some options to look after.
Answer: My problem was that I did not set my default language as the one that I wanted Windows 10 apps to be in.
For Windows 10 users:
Settings > Time & language > Region & language > Click the language that you want it to be default > Set as default
Then after you restart the Windows 10 app, it should use the default language setting.


Prevent flip fluids simulation from generating random flying particles

Question: I feel a little bit stuck on my personal project and thought that it might be helpful to ask for help here.
The thing is, I desire to make flip fluids sim flowing out of skulls eyes straight down(similar to how any liquid falls down in real life), but I just can not figure out how to force it to fall down, for some reason simulation is random and liquid is just flying out of skull's eyes instead of flowing down(check pick)...is it because of scale/world settings or must I work with force fields? Any advise?
I will attach blend file just in case anybody feels like educating me.
Thanks in advance <3
link to blender file download
Answer: If you select your domain object and checkout the physics properties under "enable surface tension" you will find:

If you hover your cursor over the question mark you will get:

so it should be clear what to do:
either uncheck surface tension...or decrease tension...or increase number of allowed max frame substeps.
Comment: I am blind. Thank you for healing my eyesight, kind man)


Apple Music splash screen won't go away!

Question: I can't get to my music on my iPad because whenever I launch the app I get a splash screen for Apple Music with no apparent buttons or links to get past it. Does anyone know how to get out of this? (Restarting the iPad doesn't seem to help.)
Comment: This has also happened to me. Seems like a bug that iOS 9.3 can hopefully work out.
Answer: This happens when the Music app cannot connect to the internet on its first startup.
Make sure the Music app can access the internet (connect to a WiFi or enable mobile data usage for the Music app in the settings). A button to skip the message will appear. Once you skip it the message won't appear a second time (at least not until you update again).
Comment: Thanks. I've tried this once without success; I'll experiment some more with WiFi and Music to see if I fare better.
Answer: I believe in Settings -> Music you can disable Apple Music.  Perhaps that would be enough to hide the splash screen and move on.
Come to think of it, the splash screen came up on my iPhone, but it asked me to log back in.  It wouldn't go anywhere after putting in my credentials.  I think I eventually went back and tapped the "not right now" link (or whatever the wording is) and got into the app.
Comment: I declined Apple Music when it first came up, and since then, at least, I've had a button in settings to "Show Apple Music." That has been disabled all along. Thanks for your suggestion; I'll look more into settings.


php redirection not working

Question: Ive got this register script that puts the information into a mysql database. now it all works fine and when someone does something wrong its says the error (e.g. "Username not defined")
but when it goes wrong it does not look very good because it just displays the message on an empty page, so i thought i would make it redirect to the form page and display the message there.
here is the working script
$forename = $_POST['forename'];
$surname = $_POST['surname'];
$email = $_POST['email'];
$password = $_POST['password'];
$username = $_POST['username'];

$errors = array();
 if(!$username) {

    $errors[] = "Username is not defined";

 }

 if(!$password) {

    $errors[] = "Password is not defined";

 }

and it continues.
now i just thought i could do this
 $errors = array();

 if(!$username) {

    $errors[] = header( 'Location: http://localhost/muiltabledistractions/#!/page_register_error-Username-is-not-defined' ) ;

 }

 if(!$password) {

    $errors[] = "Password is not defined";

 }

but no, all it does is ignore it.
could someone please help me
please feel free to ask for more of the script if you need it
many thanks connor
Comment: Did you read the [header docs](http://php.net/manual/en/function.header.php)?  The function doesn't return anything.
Answer: You cannot wrap a header in a array like that.
You just call the function, then it redirects.
header( 'Location: http://localhost/muiltabledistractions/#!/page_register_error-Username-is-not-defined' ) ;

Answer:
it does not look very good because it just displays the message on an empty page,

What's the problem?
Why not to show the form again? with fields already filled.
This is going to be a user-friendly interface.
Just include your form in the same page with fields populated.
That's more common way than your redirects to blank form.
This is called POST/Redirect/GET pattern and here goes a short example of it:
the code
<?
if ($_SERVER['REQUEST_METHOD']=='POST') {

  $err = array();
  //performing all validations and raising corresponding errors
  if (empty($_POST['name']) $err[] = "Username field is required";
  if (empty($_POST['text']) $err[] = "Comments field is required";

  if (!$err) {
    // if no errors - saving data
    // and then redirect:
    header("Location: ".$_SERVER['PHP_SELF']);
    exit;
  }  else {
    // all field values should be escaped according to HTML standard
    foreach ($_POST as $key => $val) {
      $form[$key] = htmlspecialchars($val);
    }
} else {
  $form['name'] = $form['comments'] = '';
}
include 'form.tpl.php';
?>

the template
<? if ($err): ?>
  <? foreach($err as $e): ?>

<?=$e?>

  <? endforeach ?>
<? endif ?>
<form>
  <input type="text" name="name" value="<?=$form['name']?>">
  <textarea name="comments"><?=$form['comments']?></textarea>
  <input type="submit">
</form>

Answer: You are placing the return value of the header function in an array, then continuing with your page execution.
If you don't care about anything that would normally happen below that redirection, which I believe is what you're implying, you should just set the header and then immediately exit. Do not try to place the return value of the header function into the errors array like that, as there's no point.
if(!$username) {
   header('Location: http://localhost/muiltabledistractions/#!/page_register_error-Username-is-not-defined');
    exit;
}

Answer: I don't if this is the problem, but it's important to include the status code in header too. Like:
header("Location: /foo.php",TRUE,302);

307 for Temporary Redirect, 302 for permanently moved. Chrome, a while ago, didn't accepted headers redirect without status code (i don't know nowadays).
Answer: try this after filling your error array:
if (count($errors) > 0)
{
  header( 'Location: http://localhost/muiltabledistractions/#!/page_register_error-Username-is-not-defined' );
  exit;
}

Keep in mind there should be no html output before this part!

php redirection not working


Export version history from sharepoint online using webservices

Question: I am using webservices to export web from sharepoint online.
Migration is working fine but versions are not getting migrated with the web. I am using ExportWeb method of /_vti_bin/Sites.asmx service.
Is there any OOTB method to export versions along with other content ?
Comment: i always get a number 5 Status exception. I can't save the Export file in a doclib.
Can you help me with that problem?
If i can fix this, i think my next problem is the same as yours. Perhaps we can work together on it.
Answer: Try SPServices' GetVersions function
http://spservices.codeplex.com/wikipage?title=Versions&referringTitle=%24%28%29.SPServices


Cancellation law for forward and backward images

Question: I am working on the exercise from Terence Tao's Analysis I and I wanted to verify the following proof. I have proven one side of the biimplication and am now stuck on the second part (a hint would be sufficient). Since I am self-studying mathematics I would also be happy to hear your comment on the overall structure and style of the proof.
Exercise 3.4.5 Let $X,Y$ be sets, let $f:X\to Y$. Show that $\forall S\subseteq X: f^{-1} \left(f(S)\right) = S$ if and only if $f$ is injective.
\begin{proof}
We first show that $f$ is injective implies $f^{-1} \left(f(S)\right) = S$.
We have already proven the cancellation law for bijective functions:
$$ \forall x: g^{-1} \left(g(x)\right) = x \text{ and } g \left(g^{-1}(x)\right) = x$$
We use this fact to prove this proposition. We restrict $f:X \to Y$ to the mapping $f_S$ with the domain $S$ and range $f(S)$
$$f_S: S \to f(S), \quad f_S(x)  := f(x)$$
Then $f_S$ is a function and in particular $f_S$ is bijection (Proof: Argue by contradiction. Suppose $f_S$ is not a bijection. Then by negating bijection property $\left(\forall y \in f(S) \quad \exists_{1} x \in S: f_S(x)=y \right)$ we obtain one of the following mutually exclusive cases by trichotomy of order on natural numbers:

$\exists y \in f(S) \quad \exists_{0} x \in S: f_S(x)=y$, a contradiction to the definition of the forward image $f(S):=\{f(x): x\in S\}$
$\exists y \in f(S) \quad \exists_{>1} x \in S: f_S(x)=y$, a contradiction to the injectivity assumption of $f$, since $\exists x,x' \in S: x\neq x'$ and $f_S(x)=f_S(x')$ implies $\exists x,x' \in X: x\neq x'$ and $f(x)=f(x')$.

as desired.) Since $f_S: S \to f(S)$ is bijection, we must have
$$f_S^{-1} \left(f_S(S)\right) = S$$
since by Exercise 3.6.3 we have $\forall x \in S: f_S^{-1} \left(f_S(x)\right) = x$ hence $\{ f_S^{-1} \left(f_S(x)\right): x \in S\} = \{x \in S: x \in S\} = S$. It is then left to show that
$$f_S^{-1} \left(f_S(S)\right) =  f^{-1} \left(f(S)\right)$$
The fact that $f_S(S) = f(S)$ is true since $\forall x \in S: f_S(x) = f(x)$ and injectivity of $f$ together imply $\{f(x) \in Y: x \in S\} = \{f_S(x) \in f(S): x \in S\}$.
$$f_S^{-1} \left(f(S)\right) = S$$
The fact that $f_S^{-1} \left(f(S)\right) = f^{-1} \left(f(S)\right)$ is true since $\forall y \in f(S): f_S^{-1}(y) = f^{-1}(y)$ and injectivity of $f$ imply $\{x \in X: f(x) \in f(S)\} = \{x \in S: f_S(x) \in f(S)\}$
$$f^{-1} \left(f(S)\right) = S$$
as desired.
Now we show that $f^{-1} \left(f(S)\right) = S$ implies that $f$ is injective.
proof
\end{proof}
Answer: Assume f is injective.
Quickly show A subset $f^{-1}f(A).$
Now assume x in $f^{-1}f(A).$
Thus f(x) in f(A); exists a in A with f(x) = f(a).
Conclude x = a in A.  Thus the reverse inclusion.


Prompt object is not seen in Object Manager

Question: "Prompt" Standard object is not seen in the Object Manager. But it is visible in the Developer Console -> Open resource.
Answer: We can only see objects which we can customise like creation of fields..etc in Object manager. But for Prompt we cannot create the fields or customise it .
You can use this SOQL query to check which objects can be customised.
<code>SELECT Label, QualifiedApiName FROM EntityDefinition WHERE IsCustomizable = true
</code>
Answer: In-app guidance has its own builder interface, are you looking for something in particular about the objects related to in-app guidance features? You haven't posed any question to be answered by the community in your request, only a statement.
https://help.salesforce.com/s/articleView?id=sf.customhelp_lex_prompt_add.htm&type=5


What is exactly is considered taxable income when you retire?

Question: I'm in my 30's and trying to figure out whether I should convert some of my traditional IRA funds into a Roth. The funds would be taxed at 15% based on my current taxable income. So, I need to best determine if my taxable income at retirement will be at the 15% bracket or more. What are the possible sources of taxable income when you retire besides the withdrawals from your traditional IRA acct? Are your Social Security withdrawals included in taxable income? Thanks.
Answer: The best argument I've heard about the "should I convert traditional to Roth?" is this: if you convert your traditional IRA to a Roth now - you pay your tax burden at your current marginal tax rate (or more if it bumps you into higher bracket).  If you don't convert, you pay your tax burden at your average tax rate in retirement.
For most middle-class taxpayers with enough to convert that the decision matters, I think it's very unlikely their average tax rate will be higher than their current marginal rate, so in most cases - don't do it.
This is the article making that argument (in depth, with math!):
http://www.joetaxpayer.com/images/ThinkingAboutaRoth401(k).pdf
The article's thesis is that popular financial press is wildly over-promoting the Roth, primarily through fault in the popular "side fund" analysis.
All that said - you actually have the ability to make the conversion now (by Dec 31st 2010), without paying any add'l taxes on it yet (1st payment not due until Apr 2012 for tax year 2011) and roll it back as long as you make the decision by Oct 15th 2011.  I'll see if I can find the article laying out that logic.
Comment: FWIW - I'm right in the middle of this struggle myself right now.  After reading that article, I've decided against converting for retirement purposes, though I'm still toying with the idea in order to be able to withdraw my conversion contribution (penalty free) in 5 years to invest as the down payment on a house.
Comment: glad you liked that article I discuss on my site. For those who wish to convert, I suggest 'filling up' the 15% bracket, but no more.
Answer: In regards to your question about Social Security being taxable income, yes - Social Security distributions are currently considered taxable income.  That wasn't the case for decades, but what Congress giveth, Congress can taketh away.
According to IRS tax tip 2010-31 (http://www.irs.gov/newsroom/article/0,,id=179091,00.html):
Add one-half of the total Social Security benefits you receive to all your other income, including any tax exempt interest and other exclusions from income."
If that is higher than the following (2009) base amounts, some of your benefits may be taxable:
· $32,000 for married couples filing jointly.
· $25,000 for single, separated, head of household, widow w/ dependent child
· $0 for married filing separately
So if you're single, you'd have to keep your 401k + traditional IRA distributions + 1/2 social security distributions under $25k to avoid the social security adding to your taxable income
In 2010, the 15% tax bracket stops at $34k for single filers.


Migration from existing Java EE project to maven without changing directory layout

Question: I have seen many questions concerning this issue, but I'm new to this topic and I have to convert previously written project (standard, Eclipse Java EE project) into Maven.
My first problem is that I'm completely new to Maven. Second - I can't change the directory layout. And third - I'm running out of time.
Some of topics I've read covered few of my questions, but I need it clearer.
I have 3 modules connected with each other:
* Main one with catalogues: .settings, db-schema, EarContent,
* EJB with .settings, bin, build, ejbModule
* WEB with .settings, build, src, WebContent.
As far as I know (correct me if I'm wrong) there is just one 'mapping' when I have single catalogue with source code and it looks like this:
<code><build>
    <sourceDirectory>ejbModule</sourceDirectory>
    ...
</code>
But what if I have two catalogues? I mean the WEB module - src and WebContent.
What else do I need to change if don't use standard directory layout?
What with the main module with EarContent? - There is no source code, but there is an -ds.xml file which (I guess) I have to put somewhere.
In main POM.xml I know that I have to add  tags, but is there anything else I should do?
Sorry for (maybe) not precise and wide questions, but I've started today and I have to do it fast. So far I've found Sonatype site and managed to get one of their pdfs, but I'm reading it quite too slow and need 'some' help doing it. I've also downloaded the archetype for nexus repository and I'm trying to understand it.
Answer: Try to use add-source goal of build-helper-maven-plugin.


How to cross-compile programs for the Raspberry Pi with gcc?

Question: I am fond of using gcc to compile small little C and C++ programs on my main computer.  However, I also have a Raspberry Pi, and, being a 700-MHz single-core computer, I would prefer to not have to do my development work on it every time I want to create a binary for it.  How (for I know that there's a way) do I cross-compile my program for the Raspberry Pi using my x86 laptop?  And is there a way that I may compile C(++) programs on the Pi but produce an x86 binary?  If it's any help, "The SoC is a Broadcom BCM2835. This contains an ARM1176JZFS, with floating point..." (according to the official Raspberry Pi FAQ).
Comment: There is also Raspberry PI SE, here is a question that can get you on the right track: http://raspberrypi.stackexchange.com/questions/192/how-do-i-cross-compile-the-kernel-on-a-ubuntu-host
Comment: Good answer here: [Cross-Compile for ARM?](http://askubuntu.com/q/250696/11522)
Answer: Using a combination of poking around in the apt repositories and the extremely excellent Building Embedded Linux Systems (2nd edition, 2008, O'Reilly), I found this:

arm-linux-gnueabi-gcc

That is both the name of command and the package that you install to acquire it.  Once invoked, it acts exactly as "vanilla" gcc, with the only exception that it builds packages for the ARM architecture (or a subset including the BCM2835, at least).  Building Embedded Linux Systems (pg 93-94) explains that the names used for invoking the GNU tools in a cross-compilation manner follows this format:

cpu-kernel-manufactuer-os

The -gcc at the end of the topmost example is the component, used for specifing which part of binutils you want to use.  It can be swapped out for another GNU toolchain component, such as ld (linker) or as (assembler).  For arm-linux-gnueabi-gcc, arm is the architecture, linux is the kernel, gnueabi is the os, and gcc is the component.  Where is the manufacturer?  Apparently, the manufacturer can be specified as "unknown", as it rarely makes a difference, or left out alltogether (including it would make arm-linux-unknown-gnueabi-gcc).
Comment: N.B gcc-arm-linux-gnueabihf is the package name but   arm-linux-gnueabihf-gcc  is the program name in 20.04
Answer: Officially documented method
https://www.raspberrypi.org/documentation/linux/kernel/building.md (GitHub)
git clone https://github.com/raspberrypi/tools
export PATH="$(pwd)/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin:${PATH}"
printf '#include <stdio.h>\nint main() { puts("hello world"); }\n' > hello_world.c
printf '#include <iostream>\nint main() { std::cout << "hello world" << std::endl; }\n' > hello_world.cpp
arm-linux-gnueabihf-gcc -std=c99 -o hello_world_c hello_world.c
arm-linux-gnueabihf-g++ -std=c++11 -o hello_world_cpp hello_world.cpp

Tested in Ubuntu 17.10, tools repo at 5caa7046982f0539cf5380f94da04b31129ed521
Answer: I am not sure at 100%, but, using https://tandrepires.wordpress.com/2012/08/01/raspberry-pi-openelec-pvr-dvb-t/, you could try:
1) Required libraries:
sudo apt-get install g++ git nasm flex bison gawk gperf autoconf automake m4 cvs libtool \
byacc texinfo gettext zlib1g-dev libncurses5-dev git-core build-essential xsltproc libexpat1-dev zip \
autopoint xfonts-utils libxml-parser-perl libproc-processtable-perl default-jre

2) Compile the project with the following options, where N is the number of cores of your x86 CPU:
$ PROJECT=RPi ARCH=arm PVR=yes make release -j N

I hope it helps.
`
Comment: I appreciate the effort, I really do.  Unfortunately, this tutorial (and the corresponding line of code) are for using `make` to compile a project that was set up to use make ("PROJECT=RPi ARCH=arm PVR=yes **make** release -j N", the stuff before is just a bunch of shell variables).  Now, in reality `make` _uses_ gcc, but to use the line of code provided I would have to get the source of make and then look through most of it searching for the different parts of code that would add on the necessary arguments to gcc.  Thank you for trying, though!


How good is 1. e3 2. c4 as an opening for White?

Question: How good is 1. e3 2. c4 as an opening for White? Afterward, developing the knight on b1 to c3, and developing the bishops too, it seems good. Castling is preferably done on opposite sides as well.
Comment: Seems like it transposes to the English opening, with perhaps little independent interest.
Comment: if you play it like a system, you're not playing for an advantage. But you can play it seriously, but there's a lot of transpositions and it's not an opening you want to play without much experience.
Comment: It's okay but I see no advantage over starting with 1.c4
Answer: Overall, I wouldn't suggest it, especially for a beginner. There are better ways to fight for an advantage.
By playing e3 first, you are allowing your opponent to do almost whatever they like on their first move. Are you OK with them playing 1...d5? Is that going to prevent you from playing c4? If that's going to be a problem, you may want to play 1.c4 first instead (which is the much more reputable English opening.)
With a pawn on e3, your c1 bishop has limited scope. Perhaps you want to fianchetto it to b2? Otherwise, it's either stuck on d2 where it doesn't do much, or you need to play e4 to free it, which perhaps means that e3 was a waste of a tempo.
Castling on opposite sides seems like it's something you need to decide later - don't do it if you aren't in the right position. If your opponent castles kingside (which they usually do), then castling queenside means that you're putting your king on the c-file, behind a pawn you've moved two squares (and if you've fianchettoed the c1 bishop, the b-pawn has also moved.) Depending on what your opponent has been doing and how open the game has become, this may be a bad idea.
Answer: It's difficult to assess how good a relatively unplayed opening like this when considered in isolation. However I feel it's dominated by the English. I want to play 1.c4 first, as it's directly aggressive, and leaves the door open as to how I will develop the bishops. I am unlikely to play e4 for a while, as d4 can become weak, but I don't need to play e3 yet.
The question then is: are there any risks in the English which mean I should play 1.e3 first? What countermove would mean I don't want to play 2.c4, and play something else? Actually, no Black response to 1.c4 particularly alarms me: I feel ok to play in any of the 20 positions which Black returns to me after his first move.
Domination of one strategy by another is a simplifying concept in game theory, in the absence of complete analysis. So a sufficient answer to the question: "how good is 1.e3?" Is "not as good as 1.c4!" The Nakamuras of this world will continue to play with it occasionally, but not, I suspect, against the Karlsens of this world.
Answer: Compared to what?
I played e3 myself way back then - if you manage to lure your opponent into a reverse Sicilian, especially any sharp variation where the tempo makes the difference, it's fine.§ Otherwise, hard to say. You could take a look at the Lichess opening book on the analysis board: e4 has 33/42/25%, e3 33/27/39%. But note those stats might be extremely skewed (only 687 games for e3, maybe all by the same oddball who will never learn...)
§After 1.e3 e5 2.c4 Nf6 3.Nc3 d5 4.cxd5 the stats are already 50/31/18. Even a GM game is listed, you have one guess who played White, hint: begins with N and ends with akamura. ;-)
Comment: Is it Shinsuke Nakamura, the GM?
Comment: The stats are good after 3...d5, but it seems that 3...Nc6 and 3...Bb4 are more common replies, and the stats aren't as good for those.
Comment: @DM: Exactly what I said (and what Laska said) - if Black plays a closed Sicilian, no advantage for White - thus why not playing 1.c4 in the first place...


What constructions for data authentication are subject to the birthday paradox?

Question: $H(m\mathbin\Vert k)$ as an authentication algorithm, where $H: \{0, 1\}^* \rightarrow \{0, 1\}^{n}$, has at most a strength equivalent to $\frac{n}{2}$ bits. $H((k^\prime \oplus \mathrm{opad})\mathbin\Vert H((k^\prime \oplus \mathrm{ipad})\mathbin\Vert m))$, the definition of HMAC, has an upper strength of $n$. The security of block cipher modes and block ciphers providing authentication is less clear to me. What parts of a MAC algorithm construction determine if it has a strength of $n$ bits as opposed to half that number?
Answer: It turns out that the birthday paradox figures into both the suffix-MAC $H(m \mathbin\Vert k)$ and the HMAC $H((k \oplus \mathrm{opad}) \mathbin\Vert H((k \oplus \mathrm{ipad}) \mathbin\Vert m))$, but in different ways.  And, curiously, there is no theoretical formalism in the field of 'provable security' for the way that it figures into suffix-MAC, which is the one that, as you observed, is practically relevant.
The quick summary is that, for a $b$-bit hash function $H$, when $k$ is unknown to an attacker, for suffix-MAC $H(m \mathbin\Vert k)$, the attacker can spend $2^{b/2}$ work offline to find messages $m_a \ne m_b$ that collide under $H$, whereas for HMAC, the attacker must interact online with your system for $2^{b/2}$ messages before they're expected to stumble upon messages $m_a \ne m_b$ that collide under $\operatorname{HMAC-}\!H_k$.
Because $2^{b/2}$ offline work is sometimes feasible, e.g. if $b = 128$ as in MD5 (which also has nongeneric collision attacks that reduce the work to something negligible), whereas $2^{b/2}$ online interactions with a single application is nearly unthinkable, when summarizing MAC security we usually paper it over and say that suffix-MAC has $b/2$ bits of security while HMAC has $b$ bits of security—but you'll find the gory details in papers analyzing the 'provable security' of any MAC.
In a little more detail:

The suffix-MAC construction $H(m \mathbin\Vert k)$ for an iterated hash function $H$, i.e. roughly where $H(m_0 \mathbin\Vert m_1 \mathbin\Vert \cdots \mathbin\Vert m_{n-1}) = f(\cdots(f(\mathit{IV}, m_0), m_1)\cdots, m_{n-1})$, is vulnerable to collisions in $f$: if you can find initial message blocks $m_a \ne m_b$ such that $f(\mathit{IV}, m_a) = f(\mathit{IV}, m_b) = h$, then the messages $m_a$ and $m_b$ always have the same authenticator $$H(m_a \mathbin\Vert k) = f(f(\mathit{IV}, m_a), k) = f(h, k) = f(f(\mathit{IV}, m_b), k) = H(m_b \mathbin\Vert k),$$ as do any pairs of messages that start with $m_a$ or $m_b$ and share a common prefix, $m_a \mathbin\Vert m'$ and $m_b \mathbin\Vert m'$.
An adversary who knows $f$ and $\mathit{IV}$—which are a public function and constant, respectively, in cases like SHA-256—can work offline to try to find such a collision.  Once they've found one, and they will know when they've found one because they can just test it, they may be able to break your application immediately with probability 1 and no prior interaction.
This is practically relevant: cryptosystems based on MD5 and SHA-1 were broken in practice by finding such collisions, and MD5 was even exploited to forge HTTPS certificates in a widely publicized incident of international industrial sabotage by the United States and Israel against Iran (although with RSASSA-PSS signatures, rather than with symmetric authenticators).
What's curious is that there's no theoretical formalism in the field of provable security about this.  Every fixed compression function like SHA-256 has collisions.  We just don't know any yet.  We can't say anything formal about an attacker's success probability after a certain amount of work for attacks on these constructions, because there is nothing randomized about them.  Either the attacker knows a collision (and one certainly exists) or they don't, and while we can informally conjecture about their expertise in cryptanalysis, no formalism in cryptography helps with quantifying probabilities about that knowledge.
$\operatorname{HMAC-}\!H_k$ is vulnerable to an internal collision in $H((k \oplus \mathrm{ipad}) \mathbin\Vert m)$: for every $k$, there are guaranteed to be many pairs of messages $m_a \ne m_b$ such that $$H((k \oplus \mathrm{ipad}) \mathbin\Vert m_a) = H((k \oplus \mathrm{ipad}) \mathbin\Vert m_b).$$  In that case, the two messages share a common authentication tag under the key $k$, and so if the sender provides an authentication tag for $m_a$, the attacker can replace the message by $m_b$ and leave the tag intact, and the receiver will be none the wiser.  (A collision may also happen in the outer $H$, of course.)
But the attacker can't try offline to test whether $m_a$ and $m_b$ collide under $\operatorname{HMAC-}\!H_k$, because they don't know $k$, in the formalism of provable security.  So, the attacker's best strategy (in the cases where we do have security reductions) is just to try substituting messages without changing their authentication tags, and the expected number of attempts at forgery before a collision will be about $2^{b/2}$.
The same applies to other constructions, like CMAC, and this is why, if you look closely at the security reductions for many of these constructions, you will find references to the birthday bound, and forgery probabilities in terms of numbers of queries $q$ as long as $q \lll 2^{b/2}$.  A notable exception to this is polynomial evaluation one-time MACs, which work differently, but that will have to be a bedtime story for another night.
Comment: What if the key that is used for authentication in the schemes you speak of in the last paragraph is derived from a master key and a nonce? Would the maximum number of queries still be $2^{b/2}$?
Answer: The part where you can find some way to make a collision useful in your attack.
With the first MAC, $H(m\parallel k)$ there's a simple forgery attack: Generate $(m,m')$ until $H(m)=H(m')$ with $m\neq m'$ (but same length), then submit $m$ to the signing oracle and use $m'$ as the message on which you created a forgery. Because the internal state is the same after $m$ or $m'$ is processed, the same MAC will be generated. In total this gets you away with $n/2$ offline hash evaluations. Note that this assumes that $m,m'$ have the same length which is a multiple of the block length of the Merkle-Damgård hash H.
With HMAC however, first you can't make offline evaluations of the hash because you don't know the prefix and secondly to discover the collision you'd have to query both colliding strings to the oracle at which point you can't use them anymore for submission as forgery.
For a primer on the security games, see this Q&A.
Comment: I know that it depends upon a part that the birthday paradox applies to, but *what* makes it so that it applies? CBC-MAC works just like a hash function, but why is its security not half of its output size?
Comment: @Melab I think it comes down to "can you compute a deterministic 'pre-value' to the MAC that doesn't involve the key". For CBC-MAC and HMAC and H(k||m) this is impossible.