Script to allow the creation of user cgroups at login when no systemd is present

cg.sh

#!/bin/sh
#
# Simple script that uses the cgmanager client to create cgroups upon login
# for normal users so that they can use unprivileged LXC containers during
# their session. Meant to be executed at login time with a password-less
# sudo command like this:
#
#   sudo /usr/local/bin/cg.sh create $$
#
# To be used on systems without systemd.
#
# Put the following in /etc/sudoers.d/cgm and make sure users are part of the
# "users" group:
#
#   Cmnd_Alias CGMANAGER = /usr/local/bin/cg.sh create *, \
#                          /usr/local/bin/cg.sh remove *, \
#                          /usr/local/bin/cg.sh remove
#   %users    ALL=(root) NOPASSWD:CGMANAGER
#
# Copyright (c) 2015, Alexandre Hamelin <alexandre.hamelin gmail.com>

action=$1
pid=$2

[[ -z "$SUDO_USER" ]] && exit 1

cg=$SUDO_USER

case $action in
create)
    [[ -z "$pid" ]] && exit 1
    cgm create all $cg &>/dev/null
    cgm chown all $cg $(id -u $SUDO_USER) $(id -g $SUDO_USER)
    cgm movepid all $cg $pid
    ;;
remove)
    [[ -n "$pid" ]] && {
        # Move the process back into the root cgroup.
        # Assume this location for the cgroup_root mount point.
        mnt=$(mount | awk '$1 == "cgroup_root" {print $3}')
        cd "$mnt"
        for ctrl in *; do
            echo $pid > $ctrl/tasks
        done
    }
    cgm remove all $cg
esac