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# First, make sure that cgroups are mounted correctly.
: {LOG:=stdio}
[ -d $CGROUP ] ||
mkdir $CGROUP
mountpoint -q $CGROUP ||
mount -n -t tmpfs -o uid=0,gid=0,mode=0755 cgroup $CGROUP || {
echo "Could not make a tmpfs mount. Did you use -privileged?"
exit 1
if [ -d /sys/kernel/security ] && ! mountpoint -q /sys/kernel/security
mount -t securityfs none /sys/kernel/security || {
echo "Could not mount /sys/kernel/security."
echo "AppArmor detection and -privileged mode might break."
# Mount the cgroup hierarchies exactly as they are in the parent system.
for SUBSYS in $(cut -d: -f2 /proc/1/cgroup)
mountpoint -q $CGROUP/$SUBSYS ||
mount -n -t cgroup -o $SUBSYS cgroup $CGROUP/$SUBSYS
# The two following sections address a bug which manifests itself
# by a cryptic "lxc-start: no ns_cgroup option specified" when
# trying to start containers withina container.
# The bug seems to appear when the cgroup hierarchies are not
# mounted on the exact same directories in the host, and in the
# container.
# Named, control-less cgroups are mounted with "-o name=foo"
# (and appear as such under /proc/<pid>/cgroup) but are usually
# mounted on a directory named "foo" (without the "name=" prefix).
# Systemd and OpenRC (and possibly others) both create such a
# cgroup. To avoid the aforementioned bug, we symlink "foo" to
# "name=foo". This shouldn't have any adverse effect.
echo $SUBSYS | grep -q ^name= && {
NAME=$(echo $SUBSYS | sed s/^name=//)
# Likewise, on at least one system, it has been reported that
# systemd would mount the CPU and CPU accounting controllers
# (respectively "cpu" and "cpuacct") with "-o cpuacct,cpu"
# but on a directory called "cpu,cpuacct" (note the inversion
# in the order of the groups). This tries to work around it.
[ $SUBSYS = cpuacct,cpu ] && ln -s $SUBSYS $CGROUP/cpu,cpuacct
# Note: as I write those lines, the LXC userland tools cannot setup
# a "sub-container" properly if the "devices" cgroup is not in its
# own hierarchy. Let's detect this and issue a warning.
grep -q :devices: /proc/1/cgroup ||
echo "WARNING: the 'devices' cgroup should be in its own hierarchy."
grep -qw devices /proc/1/cgroup ||
echo "WARNING: it looks like the 'devices' cgroup is not mounted."
# Now, close extraneous file descriptors.
pushd /proc/self/fd >/dev/null
for FD in *
case "$FD" in
# Keep stdin/stdout/stderr
# Nuke everything else
eval exec "$FD>&-"
popd >/dev/null
# If a pidfile is still around (for example after a container restart),
# delete it so that docker can start.
rm -rf /var/run/