github.com/dougm/docker@v1.5.0/project/dind (about)

     1  #!/bin/bash
     2  set -e
     3  
     4  # DinD: a wrapper script which allows docker to be run inside a docker container.
     5  # Original version by Jerome Petazzoni <jerome@docker.com>
     6  # See the blog post: http://blog.docker.com/2013/09/docker-can-now-run-within-docker/
     7  #
     8  # This script should be executed inside a docker container in privilieged mode
     9  # ('docker run --privileged', introduced in docker 0.6).
    10  
    11  # Usage: dind CMD [ARG...]
    12  
    13  # apparmor sucks and Docker needs to know that it's in a container (c) @tianon
    14  export container=docker
    15  
    16  # First, make sure that cgroups are mounted correctly.
    17  CGROUP=/cgroup
    18  
    19  mkdir -p "$CGROUP"
    20  
    21  if ! mountpoint -q "$CGROUP"; then
    22  	mount -n -t tmpfs -o uid=0,gid=0,mode=0755 cgroup $CGROUP || {
    23  		echo >&2 'Could not make a tmpfs mount. Did you use --privileged?'
    24  		exit 1
    25  	}
    26  fi
    27  
    28  if [ -d /sys/kernel/security ] && ! mountpoint -q /sys/kernel/security; then
    29  	mount -t securityfs none /sys/kernel/security || {
    30  		echo >&2 'Could not mount /sys/kernel/security.'
    31  		echo >&2 'AppArmor detection and -privileged mode might break.'
    32  	}
    33  fi
    34  
    35  # Mount the cgroup hierarchies exactly as they are in the parent system.
    36  for SUBSYS in $(cut -d: -f2 /proc/1/cgroup); do
    37  	mkdir -p "$CGROUP/$SUBSYS"
    38  	if ! mountpoint -q $CGROUP/$SUBSYS; then
    39  		mount -n -t cgroup -o "$SUBSYS" cgroup "$CGROUP/$SUBSYS"
    40  	fi
    41  
    42  	# The two following sections address a bug which manifests itself
    43  	# by a cryptic "lxc-start: no ns_cgroup option specified" when
    44  	# trying to start containers withina container.
    45  	# The bug seems to appear when the cgroup hierarchies are not
    46  	# mounted on the exact same directories in the host, and in the
    47  	# container.
    48  
    49  	# Named, control-less cgroups are mounted with "-o name=foo"
    50  	# (and appear as such under /proc/<pid>/cgroup) but are usually
    51  	# mounted on a directory named "foo" (without the "name=" prefix).
    52  	# Systemd and OpenRC (and possibly others) both create such a
    53  	# cgroup. To avoid the aforementioned bug, we symlink "foo" to
    54  	# "name=foo". This shouldn't have any adverse effect.
    55  	name="${SUBSYS#name=}"
    56  	if [ "$name" != "$SUBSYS" ]; then
    57  		ln -s "$SUBSYS" "$CGROUP/$name"
    58  	fi
    59  
    60  	# Likewise, on at least one system, it has been reported that
    61  	# systemd would mount the CPU and CPU accounting controllers
    62  	# (respectively "cpu" and "cpuacct") with "-o cpuacct,cpu"
    63  	# but on a directory called "cpu,cpuacct" (note the inversion
    64  	# in the order of the groups). This tries to work around it.
    65  	if [ "$SUBSYS" = 'cpuacct,cpu' ]; then
    66  		ln -s "$SUBSYS" "$CGROUP/cpu,cpuacct"
    67  	fi
    68  done
    69  
    70  # Note: as I write those lines, the LXC userland tools cannot setup
    71  # a "sub-container" properly if the "devices" cgroup is not in its
    72  # own hierarchy. Let's detect this and issue a warning.
    73  if ! grep -q :devices: /proc/1/cgroup; then
    74  	echo >&2 'WARNING: the "devices" cgroup should be in its own hierarchy.'
    75  fi
    76  if ! grep -qw devices /proc/1/cgroup; then
    77  	echo >&2 'WARNING: it looks like the "devices" cgroup is not mounted.'
    78  fi
    79  
    80  # Mount /tmp
    81  mount -t tmpfs none /tmp
    82  
    83  if [ $# -gt 0 ]; then
    84  	exec "$@"
    85  fi
    86  
    87  echo >&2 'ERROR: No command specified.'
    88  echo >&2 'You probably want to run hack/make.sh, or maybe a shell?'