Package: docker.io
Version: 1.6.0~rc4~dfsg1-1
Severity: normal
docker.io will not work if you have this in fstab
cgroup /sys/fs/cgroup cgroup defaults 0 0
But the initscript just runs, skips the cgroup mounting and doesn't tell the
user that docker will not work, or why.
It's not a bug with the package, just something it doesn't catch for people
with old systems that mounted cgroups differently.
Docker than fails and it's not super obvious to fix.
I had the above line to mount /sys/fs/cgroup in my fstab
The docker initscript in your package does already mount everything in
/sys/fs/cgroup/* just fine, but fails if the above is mounted from fstab.
No problem,
/usr/share/docker.io/contrib/check-config.sh
reports the error, but due to apparently a kernel bug, unmounting
/sys/fs/cgroup as cgroup, making one as tmpfs, and trying to mount the
cgroup subdirs fails with:
mount: cgroup is already mounted or /sys/fs/cgroup/cpuset busy
cgroup is already mounted on /sys/fs/cgroup
I finally found on the net that there seems to be no fix but rebooting
and sure enough, rebooting fixed this.
I have kernel 3.19, and I can swear that I had no cgroups mounted anywhere when
I
got this error.
It could be useful for the docker initscript to detect this, and give an
error message to remove the fstab line, and tell the user to reboot (for
real) to clear the cgroup state in the kernel and allow subdir cgroup
mounts.
This is the unfixed kernel bug:
https://bugzilla.kernel.org/show_bug.cgi?id=60795
The same bug also happens in reverse:
docker is working, unmount cgroups
legolas:~# umount /sys/fs/cgroup/*
legolas:~# /etc/init.d/docker stop
[ ok ] Stopping Docker: docker.
legolas:~# umount /sys/fs/cgroup
legolas:~# mount -t cgroup cgroup /sys/fs/cgroup
mount: cgroup is already mounted or /sys/fs/cgroup busy
legolas:~# grep cgroup /proc/mounts
legolas:~#
Thanks,
Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
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