tar is for tape archive and it is stream based. tar can't go backward to erase what it has already written. So, that message is to tell you that what's in the archive may not be consistent as it changed while being written.

What happens is that for each file, tar writes a header that includes the path to the file, metadata (ownership, permission, time...) and the size (n bytes) and then proceeds to dump those n bytes by reading it from the file. If the size of the file changes while tar is dumping its content, tar can't go back and change the header to say, no after all the size was not n but p. All it can do is truncate the content to n bytes if p is greater than n or pad with zeros if it's smaller.

In both cases, you'll get an error message.

tar -c Error Messages and Source Files?
I have just completed my PhD. Although my examiners did not raise any concerns, I have been grappling with an ethical issue for the entire duration of my candidature. 

The issue concerns professional knowledge of the field on which my research is based. This is an issue of concern because I am employed in the field and have access to information that is generally not publicly available (but is available to me as an employee) or only found in hard-to-get industry publications (e.g. newsletters). These publications are hard-to-get because of their specialised nature and limited circulation. 

Disclosing this information creates a potential conflict of interest for me (because of reasons associated with commercial-in-confidence, breach of trust etc.). It gets even worse because I am often actively involved in generating this information as part of various negotiations I am required to have with third parties (in my capacity as an employee). As an example, I draft policy speeches for my CEO so this has the effect of quoting my own work in my dissertation (but attributed to my CEO in the citation and bibliography!)  

To resolve this matter, I have declared (categorically) this conflict of interest (several times in my dissertation) (although I don't identify myself as the ghost writer). I have also put whatever information I thought could be ethically disclosed in the relevant context (e.g. cited the publicly available newsletter, where possible). This was to ensure future researchers could benefit from this 'inside' knowledge. I have stated this as one of the contributions to knowledge that my dissertation is making.

I must add that the professional knowledge does not contradict or undermine my research, so I am certainly not withholding the information for this reason. On the contrary, this information enhances the main arguments of my study (so omitting it presents a significant dilemma for me).

i would love to hear how else could this matter be resolved.
