[ACL-Devel] tar file format?

[Linda Walsh]

> > Hm. This seemed to be very bad idea. Acls, CAP, MAC etc should be _in_ tar archive,
> > so this info can be safely backed up and restored (possible in different machine)
> > without any addition files.  What is tar? -- it is just a collection of files (and
> > attributes) that resides in one (!) another archive file, and this another file is
> > good to backups, transfers etc etc.  _One_ file.  One possible solution is to merge
> > that /tmp/.foo into resulting tar archive, but this is not perfect (as tar format
> > stores all related file info with file, so that it will not need to seek inside
> > archive to restore all file info (esp. on tapes), and even if so, /tmp/.foo will
> > become an implementation detail).
> 
> Actually, the /tmp/.foo file is in the archive. AFAIK it's just a magic filename
> the Irix version recognizes as such. Ordinary tars , and thus just generate a
> file in the /tmp directory. Which is also quite ugly.
---
	It's only ugly if you expand an attr-containing tar with a tar that doesn't
know about attr's.  It is a way of providing compatibility without any new 
introductions of types and w/o error messages.

> 
> Another choice would be to use regular file records with identical filename for
> both, and recognize the difference by another special value (such as a date
> stamp in 1970). This would work perfectly for regular files, but would cause
> trouble for directories. We would need to prepend these special blocks for
> files, but append them to directories in tar archives so that older tars don't
> puke. Yuck!
---
	Buh buh....hmmm.  Prepending for filenames may be satisfactory,  but a user
has just extracted a directory that is marked r-x, they'll still see a perplexing 
error message.  Hey...the tmp name could be a on the fly generated 'GUID' to reduce
chances of collisions...:-)  But since only a privileged user can restore files w/MAC or
CAP

> Also, it's not portable to use binary representations. We can use the textual
> representations defined in 1003.1e.
---
	Isn't there an option to tar to store all data in ascii for portability as well
as an option to store binary for saving space?

-l
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