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Re: [Bug-tar] [PATCH] Extended attribute support for tar

From: Joerg Schilling
Subject: Re: [Bug-tar] [PATCH] Extended attribute support for tar
Date: Thu, 03 Aug 2006 00:59:31 +0200
User-agent: nail 11.2 8/15/04

James Antill <address@hidden> wrote:

>  Hi, I've created support for creating/extracting SELinux/user/root
> xattrs in GNUtar. If you have some free time, I'd appreciate anyone
> looking over the patch and letting me know if anything needs to change
> for inclusion.
>  The patch is currently based against the version in Fedora Core
> rawhide. And I've not even compiled it on a non-Linux system, so I
> imagine that some autoconf stuff needs to be added.
>  Known "issues":
> 1. ACL support isn't included, this might only be a couple of lines on
> top of the patch.

If you like to implement ACLs in a decent way, you need to implement a lot 

> 2. No tests.
> 3. No documentation (outside of --help) for the --xattrs and --selinux
> options.

> 4. xattr's are stored internally with the full xheader name, which is
> exposing internal details.

> 5. Only supports the star "SCHILY.xattr.*" format, AIUI there's a real
> POSIX format.

No, the term "POSIX format" as used by GNU tar is extremely missleading.

Any tar format that is POSIX.1-1988 compliant is a "POSIX archive"

POSIX.1-2001 defines the "pax" format.

GNU tar by default creates pre-POSIX.1-1988 archives.

In any case, be very careful!

The "SCHILY.xattr.*" format has been called "transient" and obsolete from
the beginning. It is limited to the limited Linux xattr implementation.
It has only be imple,ented as a curtesy for Linux users....

Once star adds support for a generic xattr format (e.g. one similar to what
Solaris supports), the limited "transient" format will be given up.

See the format description:


> 6. Not entirely sure what to do when SELinux/xattr's aren't supported
> when doing the extraction ... atm. tar just ignores it.

tar does not support this. Do you talk abnout star?

> 7. Currently tar defaults to not doing anything when creating an
> archive, so you need to pass --xattrs or --selinux to get all xattrs or
> just SELinux context information in the archive. This is mainly because
> of the way versions of GNUtar without this patch react.

Be careful, GNU tar by default still does not create POSIX compliant 

> 8. AIUI star only includes the headers when using it's special exustar
> format, the patch I've done for GNUtar just includes it on the else
> clause of:

This is wrong, You are only allowed to add these headers if you use "pax" or 


 EMail:address@hidden (home) Jörg Schilling D-13353 Berlin
       address@hidden                (uni)  
       address@hidden     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily

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