Re: [Vserver] tagxid mount option

From: Herbert Poetzl <>
Date: Thu 02 Feb 2006 - 10:47:04 GMT
Message-ID: <>

On Thu, Feb 02, 2006 at 07:59:18AM +0100, J.Paechnatz wrote:
> Herbert Poetzl schrieb:
> >how did you try?
> >(i.e. what filesystem, which partition, what options)
> /dev/sda1 / ext3
> defaults,tagxid,errors=remount-ro 0 1
> gives failures on reboot, leaving / unaccessible, I have to
> boot from cdrom and correct (remove the tagxid option) the fstab.

well, that's a problem with your distro basically ...

here a short explanation _what_ happens:

 - the 'root' filesystem is specified in the bootloader
   (usually with the root=/dev/xy option)

 - the 'initial' root is probably a initrd or initram disk
   which loads a few drivers and sets up a few things

 - when the fstab is examined, either from the ram disk
   or from the real root system, the filesystem is already
   mounted, and only a _remount_ with certain options

 - remounting filesystems with the tagxid option is
   _intentionally_ disabled, because it would leave
   your filesystem in an unknown state (i.e. some inodes
   tagged, others untagged)

now, why are we so cruel and/or why isn't it documented
how to do that with the rootfs, which obviously should
be possible? again the reasons are simple:

 - it isn't trivial to do so, because every distro uses
   a slightly different init method (in the ramdisk)

 - it is ill advised to tag the root filesystem of the
   host, potentially causing administrative data to
   become tagged, introducing new and unexpected
   permission issues

so, yes it is possible to mount the rootfs tagxid, but
no, we do not suggest to do so ... we _always_ strongly
advise to have a _separate_ partition (or several of
them) for the guests, to ensure that everything works
as expected ...

and yes, I know that many folks nowadays have _everything_
on a single partition, which I personally consider _very_
dangerous, and I'm not speaking about the guest partition
here ...

> >>I want to set context disk limits with vdlimit, therefore I need the
> >>tagxid mount option, did I get it right? how do I enabled tagxid
> >>support? kernel option uid24/gid24 is set.
> >
> >
> >yes, usually it's just a matter of:
> >
> >mount -o tagxid /dev/some /vservers
> does not work too. gives a german error message, meaning already mounted
> or invalid option.

well, that has two reasons:

 - the beforementioned check which does not permit to
   remount a (mounted) partition with tagxid

 - your locale setting and your (probably german)
   installation :)


> cu joh.
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Received on Thu Feb 2 10:47:45 2006

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