Extended headers (ustar format)

[Andreas Gruenbacher]

Dear all,

I just saw the ustar format includes Extended Headers in the current Austin
Group Draft 3 Commands & Utilities document. This allows to store arbitrary file
attributes as name/value pairs.

Are there any efforts to standardize the formats that shall be used for data
defined by POSIX 1003.1e DS17? Both the attribute names and values need to be
consistent across platforms.

There's a reserved attribute name prefix `security' that seems to be reserved
for 1003.1e or whatever emerges from it. Vendor specific extensions are also
allowed.

For ACLs I'd be inclined to using a format derived from the ACL text form
representation `user::rwx,user:joe:rwx,group::r-x,mask:rwx,other:r-x'.

The ustar format has the nice property that it can store both user/group names
and their identifiers in archives (plus the option to restore files by
identifiers rather than names). I think this is worth adopting for ACLs. We
would arrive at something like:
`user::rwx,user:102=joe:rwx,group::r-x,mask:rwx,other:r-x'.

Regards,
Andreas

------------------------------------------------------------------------
 Andreas Gruenbacher, a.gruenbacher at computer.org
 Contact information: http://www.bestbits.at/~ag/
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