[Devel] Re: LXC container, unmounting unneeded mount points (from the container namespace)
Michael H. Warfield
mhw at WittsEnd.com
Mon Jan 11 19:54:09 PST 2010
Added lxc-devel to the cc list since this seems to be more appropriate
over there (maybe) and I've just joined that one as well.
On Fri, 2010-01-08 at 15:35 +0100, Daniel Lezcano wrote:
> Ciprian Dorin, Craciun wrote:
> > On Fri, Jan 8, 2010 at 4:17 PM, Daniel Lezcano <daniel.lezcano at free.fr> wrote:
> >
> >> Ciprian Dorin, Craciun wrote:
> >>
> >>> Hy all!
> >>>
> >>> Today I've started to play with the LXC containers, and I've got a
> >>> question: when starting a container (with it's own mount point
> >>> namespace), and I do a `cat /proc/mounts` I also see the mount points
> >>> from my host system.
> >>>
> >>> So the question is: how can I force `lxc-create` to remove any
> >>> uneeded mount points (maybe all)?
> >>>
> >>>
> >> Committed today :)
> >>
> >> http://git.lab.toulouse-stg.fr.ibm.com/?p=lxc.git;a=commit;h=ed83715df7666879116d1657b1dd54a8fc6513f6
> >>
> Oops, this one:
> http://lxc.git.sourceforge.net/git/gitweb.cgi?p=lxc/lxc;a=commit;h=bf601689a9e0cea1ceaf17e4f7f853f5392c2827
Nice. This is EXACTLY what I've been looking for as well. Only problem
is... It didn't work. It complains about:
lxc-start: could not umount 1 mounts"
Then terminates saying it can't start the container.
When I throw in some debugging prints, I find out that it's complaining
that it can't umount {pivotdir}/dev. Commented out the return -1's in
that routine so it starts the container anyways and jump into the
running container and I discover that {pivotdir}/dev/shm is still
mounted even though it thinks it umounted it. I can see from the
debugging prints that it seems to have successfully umount it (the
debugging message indicates that it umounted it - so it saw it had it
and tried and got a good return from the attempt) but it's apparently
still mount. If I umount that {pivotdir}/dev/shm inside the container,
I can then umount {pivotdir}/dev and {pivotdir}.
Tried it both by defining lxc.pivotdir and by letting it choose a
temporary one. Tried two different containers. Same result.
This is what I get with the "return -1"'s commented out in the function
and laced with my own debugging prints to print each step of the umount
loop (this is with lxc.pivotdir = /rootfs):
===
[root at Berserker-Base ~]# lxc-start -n 1009
still mounted '/rootfs/dev'
umounted '/rootfs/dev/pts'
umounted '/rootfs/dev/shm'
still mounted '/rootfs/proc'
umounted '/rootfs/proc/bus/usb'
umounted '/rootfs/proc/sys/fs/binfmt_misc'
umounted '/rootfs/sys'
umounted '/rootfs/home'
still mounted '/rootfs/var'
umounted '/rootfs/var/lib/cgroup'
umounted '/rootfs/var/lib/nfs/rpc_pipefs'
umounted '/rootfs/usr'
umounted '/rootfs/boot'
still mounted '/rootfs/srv'
umounted '/rootfs/misc'
umounted '/rootfs/net'
still mounted '/rootfs/srv/lxc/root/1009'
umounted '/rootfs/srv/lxc/root/1009/export'
umounted '/rootfs/srv/lxc/root/1009/srv/shared'
umounted '/rootfs/srv/lxc/root/1009/dev/pts'
umounted '/rootfs/srv/lxc/root/1009/proc'
umounted '/rootfs/srv/lxc/root/1009/sys'
umounted '/rootfs/srv/lxc/root/1009/dev/shm'
umounted '/rootfs/srv/lxc/root/1009/dev/console'
umounted '/rootfs/srv/lxc/root/1009/dev/tty1'
umounted '/rootfs/srv/lxc/root/1009/dev/tty2'
umounted '/rootfs/srv/lxc/root/1009/dev/tty3'
umounted '/rootfs/srv/lxc/root/1009/dev/tty4'
umounted '/rootfs/srv/lxc/root/1009/dev/tty5'
umounted '/rootfs/srv/lxc/root/1009/dev/tty6'
still mounted '/rootfs/dev'
umounted '/rootfs/proc'
umounted '/rootfs/var'
still mounted '/rootfs/srv'
umounted '/rootfs/srv/lxc/root/1009'
still mounted '/rootfs/dev'
umounted '/rootfs/srv'
still mounted '/rootfs/dev'
lxc-start: could not umount 1 mounts
lxc-start: Device or resource busy - could not unmount old rootfs
INIT: version 2.86 booting
===
Container now continues to boot, since I commented out the error
returns. Jumping into that container:
===
[root at Berserker ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 288433504 240305660 33476248 88% /
/dev/sda6 2063504 662116 1296568 34% /rootfs
udev 1031280 200 1031080 1% /rootfs/dev
/dev/shm 1031280 0 1031280 0% /rootfs/dev/shm
/dev/mapper/VolGroup00-LogVol00
288433504 240305660 33476248 88% /
/dev/sda6 2063504 662116 1296568 34% /export
/dev/sda7 693727244 554704408 103783460 85% /srv/shared
none 1031280 0 1031280 0% /dev/shm
[root at Berserker ~]# umount /rootfs/dev/shm
[root at Berserker ~]# umount /rootfs/dev
[root at Berserker ~]# umount /rootfs
[root at Berserker ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 288433504 240305672 33476236 88% /
/dev/mapper/VolGroup00-LogVol00
288433504 240305672 33476236 88% /
/dev/sda6 2063504 662116 1296568 34% /export
/dev/sda7 693727244 554704408 103783460 85% /srv/shared
none 1031280 0 1031280 0% /dev/shm
===
Of course we also have the strange "rootfs" entry there as well.
Host system is Fedora 12.
Host kernel is: 2.6.31.9-174.fc12.i686
Guest system in each case is CentOS 5.4
Regards,
Mike
--
Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw at WittsEnd.com
/\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
NIC whois: MHW9 | An optimist believes we live in the best of all
PGP Key: 0x674627FF | possible worlds. A pessimist is sure of it!
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