Subject: Problems using a shared directory mounted into two VServers with XID tagging enabled.
From:Marcus Mülbüsch <m.muelbuesch@googlemail.com>
Date: Tue, 12 Jul 2011 14:11:42 +0200

Hello all,

    to use Disk limits I activated XID tagging, following the guide 
here: http://linux-vserver.org/Disk_Limits_and_Quota

    Now I have two VServers-Guests that share a directory, mounted in 
both vservers. The first VServer-Guest just writes there, the other 
reads and writes.

   Now, when the first vserver writes a file into that directory, the 
second one cannot read it - no wonder, "lsxid" shows the file tagged 
with the "wrong" context.

    I see three possible solutions:

    1) Mounting the shared directory on a filesystem that is not enabled 
for XID tagging. Alas, that would also mean that I cannot use Disk 
Quotas here.

    2) The second VServer-Guest is allowed to read and modify all files 
in that directory, regardless of the context the file is tagged with. 
However, I have no idea how to accomplish that. Plus, I don't know how 
disk quotas now will work.

    3) The first vserver-guest writes the files by using the context of 
the second vserver-guest. That means that the quota of the second guest 
applies. This is my preferred solution, but again I have no idea how to 
accomplish that.

    Can someone put me on the right track? Mounting the filesystem in 
/etc/vservers/<name>/fstab with a mount option perhaps?

Thanks,

Marcus