3.10 kernel comes with proper hierarchical enforcement of devices
cgroup. To keep that code somewhat sane, certain things are not
allowed. Switching from default-allow to default-deny and vice versa
are not allowed when there are children cgroups. (This *could* be
simplified in the kernel by checking that all child cgroups are
unpopulated, but that has not yet been done and may be rejected)
The mountcgroup hook causes lxc-start to break with 3.10 kernels, because
you cannot write 'a' to devices.deny once you have a child cgroup. With
this patch, (a) lxcpath is passed to hooks, (b) the cgroup mount hook sets
the container's devices cgroup, and (c) setup_cgroup() during lxc startup
ignores failures to write to devices subsystem if we are already in a
child of the container's new cgroup.
((a) is not really related to this bug, but is definately needed.
The followup work of making the other hooks use the passed-in lxcpath
is still to be done)
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
This hook script updates the hostname in various files under /etc in the
cloned container. In order to do so, the old container name is passed in
the LXC_SRC_NAME environment variable.
Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
1. deeper hierarchy has steep performance costs
2. init may be under /init, but containers should be under /lxc
3. in a nested container we like to bind-mount $cgroup_path/$c/$c.real
into $cgroup_path - but task 1's cgroup is $c/$c.real, so a nested
container would be in $c/$c.real/lxc, which would become
/$c/$c.real/$c/$c.real/lxc when expanded
4. this pulls quite a bit of code (of mine) which is always nice
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
We've been shipping those two hooks for a while in Ubuntu.
Yesterday I reworked them to use the new environment variables and
avoid hardcoding any path that we have available as a variable.
I tested both to work on Ubuntu 13.04 but they should work just as well
on any distro shipping with the cgroup hierarchy in /sys/fs/cgroup and
with ecryptfs available.
Those are intended as example and distros are free to drop them, they
should however be working without any change required, at least on Ubuntu.
Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
