@@ -27,6 +27,31 @@ do

 	[ -d $CGROUP/$SUBSYS ] || mkdir $CGROUP/$SUBSYS

 	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=//)

+		ln -s $SUBSYS $CGROUP/$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

 done

 # Note: as I write those lines, the LXC userland tools cannot setup