#!/bin/bash
 

 # DinD: a wrapper script which allows docker to be run inside a docker container.
 # Original version by Jerome Petazzoni <jerome@dotcloud.com>
 # See the blog post: http://blog.docker.io/2013/09/docker-can-now-run-within-docker/
 #
 # This script should be executed inside a docker container in privilieged mode
 # ('docker run -privileged', introduced in docker 0.6).
 
 # Usage: dind CMD [ARG...]
 

 # First, make sure that cgroups are mounted correctly.
 CGROUP=/sys/fs/cgroup
 
 [ -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
 then
     mount -t securityfs none /sys/kernel/security || {
 	echo "Could not mount /sys/kernel/security."
 	echo "AppArmor detection and -privileged mode might break."
     }
 fi
 

 # Mount the cgroup hierarchies exactly as they are in the parent system.
 for SUBSYS in $(cut -d: -f2 /proc/1/cgroup)
 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
 # 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 *
 do
 	case "$FD" in
 	# Keep stdin/stdout/stderr
 	[012])
 		;;
 	# Nuke everything else
 	*)
 		eval exec "$FD>&-"
 		;;
 	esac
 done

 popd >/dev/null

 # Mount /tmp
 mount -t tmpfs none /tmp
 

 [ "$1" ] && exec "$@"
 echo "You probably want to run hack/make.sh, or maybe a shell?"