[lxc-devel] "Shutdown" LXC container

[Tobias Gruetzmacher]

Hi,

it bugged me that there is no "clean" way to shut down a full system
container from the outside, so I wrote the attached helper script.

It finds the "init" process for the container and sends the INT signal
to that process, which most init systems (all?) interpret as a request
to reboot the system. Changing the inittab (or whatever is cool with
current init systems) to make the system halt instead gives us a nice
way to shut down a container in a clean fashion.

Since this script may be usable for system shutdown scripts, I also
implemented a timeout, but maybe lxc-wait should be extended to provide
that functionality...

Thoughts, comments?

Greetings, Tobi

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#!/bin/sh
# set -ex

usage() {
	echo "Usage: $(basename $0) {--name|-n} <name> [{--wait|-w} <timeout>]"
}

help() {
	usage
	echo
	echo "send the INT signal to a specified container"
	echo "to simulate Ctrl+Alt+Del for a clean shutdown"
	echo
	echo "Options:"
	echo "name  : name of the container"
	echo "help  : this current help."
	echo "wait  : wait <timeout> seconds for the container to stop."
	echo
	echo "For proper operation the ctrlaltdel action of the"
	echo "container should halt the system."
}

name=
waittime=
for i in "$@"; do
	case $i in
		-h|--help)
			help; exit 1;;
		-n|--name)
			name="$2"; shift 2;;
		-w|--wait)
			waittime="$2"; shift 2;;
	esac
done

if [ -z "$name" ]; then
	usage
	exit 1
fi

cgroups=$(mount -l -t cgroup)
cgroup_path=""

for i in "$cgroups"; do
    set -- $i
    cgroup_name=$1
    cgroup_path=$3

    if [ "$cgroup_name" = "lxc" ]; then
        break;
    fi

done

if [ -z "$cgroup_path" ]; then
    echo "no cgroup mount point found"
    exit 1
fi

init_pid=
while read pid
do
    set -- $(cat /proc/$pid/stat)
    ppid=$4
    if ! grep -q $ppid "$cgroup_path/$name/tasks"
    then
        init_pid=$pid
        break
    fi
done < "$cgroup_path/$name/tasks"

if [ -z "$init_pid" ]; then
    echo "no process found for '$name'"
    exit 1
fi

kill -s INT $init_pid

if [ "$waittime" ]; then
	while [ "$waittime" -gt 0 ]; do
		if lxc-info -n "$name" | grep -q 'is STOPPED'
		then
			exit 0
		fi
		sleep 1
		waittime=$((waittime - 1))
	done
	exit 1
fi
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