<story><title>Debian still having trouble with merged /usr</title><url>https://lwn.net/SubscriberLink/890219/79e54e3aab20bd87/</url></story><parent_chain><item><author>nickcw</author><text>Just in case anyone is wondering why we had (or used to have) &amp;#x2F;bin and &amp;#x2F;sbin directories as well as &amp;#x2F;usr&amp;#x2F;bin &amp;#x2F;usr&amp;#x2F;sbin here is my understanding of it.&lt;p&gt;It is because on old Unix systems there frequently wasn&amp;#x27;t enough space to store &amp;#x2F;usr on the root disk. Therefore &amp;#x2F;usr was a separate disk which might not be available during boot. This meant that you needed to put all the binaries you needed for boot in &amp;#x2F;bin and &amp;#x2F;sbin because &amp;#x2F;usr&amp;#x2F;bin and &amp;#x2F;usr&amp;#x2F;sbin might not be mounted yet.&lt;p&gt;This no longer makes sense in the days of large disks which fit &amp;#x2F;usr just fine and initrds which can mount all the disks before kicking off the things which might need those binaries. In fact I think the initrd has taken the place of &amp;#x2F;bin and &amp;#x2F;sbin on a modern system containing copies of all the binaries needed to mount the disks (like mount and fsck).</text></item></parent_chain><comment><author>Beltalowda</author><text>&amp;gt; It is because on old Unix systems there frequently wasn&amp;#x27;t enough space to store &amp;#x2F;usr on the root disk.&lt;p&gt;It was really a single system in 1971 that kicked off this trend. Originally &amp;#x2F;usr was for user files, like &amp;#x2F;home is today (do you&amp;#x27;d have &amp;#x2F;usr&amp;#x2F;dmr, &amp;#x2F;usr&amp;#x2F;ken, etc.) &amp;#x2F; and &amp;#x2F;usr were two physical disks, and at some point the &amp;#x2F; disk (a 1 or 2MB disk IIRC) was full to they put some things from &amp;#x2F;bin in &amp;#x2F;usr&amp;#x2F;bin as a hack. And it&amp;#x27;s &amp;quot;stuck&amp;quot; since then. This is why &amp;#x2F;usr has such a weird name, because it was intended for user files (&amp;#x2F;system, &amp;#x2F;software, &amp;#x2F;additional or something would make more sense, abbreviated to &amp;#x2F;sys, &amp;#x2F;sw, or &amp;#x2F;add of course). Initially Unix was a quickly developing system for internal use, but it &lt;i&gt;was&lt;/i&gt; actually used and there was often some tension between &amp;quot;do the right thing&amp;quot; vs. &amp;quot;don&amp;#x27;t break too much&amp;quot;. Some of the weird things in C are due to that as well (e.g. &amp;amp;&amp;#x27;s precedence being a good example).&lt;p&gt;I guess some other systems that ran Unix ran in to similar problems, but by the time unix started to gain some adoption in the mid to late 70s disks were larger too, so I don&amp;#x27;t know if it was ever really needed beyond that initial research unix system used only internally at Bell Labs. I believe they updated the disks on the original Unix system not too long after this making this hack superfluous, but they kept it for compatibility (and because it might be useful again in the future).</text></comment>
<story><title>Debian still having trouble with merged /usr</title><url>https://lwn.net/SubscriberLink/890219/79e54e3aab20bd87/</url></story><parent_chain><item><author>nickcw</author><text>Just in case anyone is wondering why we had (or used to have) &amp;#x2F;bin and &amp;#x2F;sbin directories as well as &amp;#x2F;usr&amp;#x2F;bin &amp;#x2F;usr&amp;#x2F;sbin here is my understanding of it.&lt;p&gt;It is because on old Unix systems there frequently wasn&amp;#x27;t enough space to store &amp;#x2F;usr on the root disk. Therefore &amp;#x2F;usr was a separate disk which might not be available during boot. This meant that you needed to put all the binaries you needed for boot in &amp;#x2F;bin and &amp;#x2F;sbin because &amp;#x2F;usr&amp;#x2F;bin and &amp;#x2F;usr&amp;#x2F;sbin might not be mounted yet.&lt;p&gt;This no longer makes sense in the days of large disks which fit &amp;#x2F;usr just fine and initrds which can mount all the disks before kicking off the things which might need those binaries. In fact I think the initrd has taken the place of &amp;#x2F;bin and &amp;#x2F;sbin on a modern system containing copies of all the binaries needed to mount the disks (like mount and fsck).</text></item></parent_chain><comment><author>ntauthority</author><text>Adding to this historical reasoning, it is to be noted that in traditional Unix, &amp;#x2F;usr was pretty much the equivalent of &amp;#x2F;home in Linux systems: the parent directory for user home directories, i.e. &amp;#x27;usr&amp;#x27;.&lt;p&gt;The existence of &amp;#x2F;usr&amp;#x2F;bin can probably be explained by the reasoning that, just like nowadays Linux systems often have a really big &amp;#x2F;home partition, early Unix systems eventually ran out of space for whatever volume would hold &amp;#x2F;bin, and with &amp;#x27;reinstalling&amp;#x27; not remotely as easy an option as it would be these days, storing an extra &amp;#x27;bin&amp;#x27; etc. directory in the &amp;#x27;larger partition for user directories&amp;#x27; became commonplace.</text></comment>