How to properly "halt" virtual machine in LXC

While running a number of virtual machines in LXC you might need gracefully shutdown each virtual machine while host reboot. Here is a script (file /usr/local/sbin/lxc-shutdown):

#!/bin/sh

name=$1
timeout=15

if lxc-info -n $name | grep -qs "STOPPED"
then
    echo $name not running...
    exit 0
fi                                           
                                                                               
ssh $name halt &                                                               
#if [ -e /usr/bin/lxc-halt ]; then                                             
#    /usr/bin/lxc-halt -n $name                                                
#else                                                                          
#    ssh $name halt &                                                          
#fi

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

lxc-stop -n $name
lxc-wait -n $name -s 'STOPPED'

This approach requires root to have password-less ssh login (see more here). So now that you have a script that let you halt gracefully virtual machine, let make few changes to /etc/init.d/lxc (somewhere around line 56):

# ...
    stop)
    log_daemon_msg "Stopping $DESC"
    #action_all "lxc-stop -n"
    # Uncomment below if you need to halt containers 
    # in reverse order
    CONTAINERS=`echo $CONTAINERS | tac -s ' '`
    action_all "lxc-halt"
    ;;
# ...

Use the following two commands to override lxc-shutdown for lxc v0.8+

                                           
update-alternatives --install /usr/bin/lxc-shutdown \                        
   lxc-shutdown /usr/local/sbin/lxc-shutdown 1                                
update-alternatives --set lxc-shutdown \                                     
   /usr/local/sbin/lxc-shutdown