I start a QEMU/KVM Ubuntu 15.10 virtual machine on boot and let it run in the background (as webserver).
What happens now if I shut down the host (also 15.10)?
Will it kill the VM and result in a virtual power cut or even worse?
Or will it trigger a "power-button-pressed" event in the VM and wait for it to shut down cleanly?
The guest system is set up to shut down properly when such a "power-button-pressed" event occurs. It's off after less than 5-10 seconds usually.
If the default behaviour on host shutdown is to kill the VM, how can I change this to a clean shutdown of the guest and waiting until it's off?
2 Answers
With the help of @Serg's answer, I crafted this set of three scripts (Python 3 and Bash) which listens for Unity Shutdown/Logout dialogs, checks for running VMs, blocks the Unity dialog, displays a nice progress bar, waits until all VMs are off or the timeout is reached, asks if remaining VMs should be forcibly killed and finally displays a custom shutdown/logout dialog.
Here are the scripts. Place them in a location contained in the $PATH variable, like /usr/local/bin/. Make sure they're owned by root and have all execution bits set (chmod +x).
vm-terminator (in Bash, the GUI):
#! /bin/bash
# Use first command-line argument as timeout, if given and numeric, else 30 sec
if [ "$1" -eq "$1" ] 2> /dev/null then timeout=$1 else timeout=30
fi
# Define function to ask whether to shut down / log out / reboot later.
function end_session () { action=$(zenity --list --title="VM Terminator" --text="All VMs are shut down. What to do now?" --radiolist --hide-header --column="" --column="" TRUE "Log out" FALSE "Reboot" FALSE "Shut down") case $action in "Log out") gnome-session-quit --logout --no-prompt ;; "Reboot") systemctl reboot ;; "Shut down") systemctl poweroff ;; *) echo "Not ending current session." ;; esac
}
# Try to shut down VMs with
( set -o pipefail shutdown-all-vms -i 0.5 -t $timeout -z | zenity --progress --title="VM Terminator" --auto-close --auto-kill --width=400
) &> /dev/null
succeeded=$?
# Evaluate whether the task was successful and show host shutdown/logout dialog or kill/manual dialog or error message.
case $succeeded in 0) end_session ;; 1) zenity --question --title="VM Terminator" --text="The timeout was reached.\n\nWould you like to forcibly power off all remaining VMs\nor abort and take care of them yourself?" --ok-label="Kill them!" --cancel-label="I'll do it myself" --default-cancel if [ $? == 0 ] then shutdown-all-vms -t 0 -k end_session else exit 1 fi ;; 129) zenity --question --title="VM Terminator" --text="You cancelled the timeout.\n\nWould you like to forcibly power off all remaining VMs\nor abort and take care of them yourself?" --ok-label="Kill them!" --cancel-label="I'll do it myself" --default-cancel if [ $? == 0 ] then shutdown-all-vms -t 0 -k end_session else exit 1 fi ;; *) zenity --error --title="VM Terminator" --text="An error occured while trying to shut down some VMs. Please review them manualy!" exit 2 ;;
esacshutdown-all-vms (in Python 3, the core):
#! /usr/bin/env python3
# Script to gracefully shut down all running virtual machines accessible to the 'virtsh' command.
# It was initially designed for QEMU/KVM machines, but might work with more hypervisors.
# The VMs are tried to be shut down by triggering a "power-button-pressed" event in each machine.
# Each guest OS is responsible to shut down when detecting one. By default, some systems may just show
# an user dialog prompt instead and do nothing. If configured, this script can turn them off forcibly.
# That would be similar to holding the power button or pulling the AC plug on a real machine.
# This script exits with code 0 when all VMs could be shut down or were forced off at timeout.
# If the 'virsh shutdown VM_NAME' command returned an error, this script will exit with error code 1.
# On timeout with KILL_ON_TIMEOUT set to False, the script will exit with error code 2.
# If KILL_ON_TIMEOUT is active and the timeout was reached, but one of the 'virsh destroy VM_NAME' commands
# returned an error, this script exits with error code 3.
import subprocess
import time
from optparse import OptionParser
# Function to get a list of running VM names:
def list_running_vms(): as_string = subprocess.check_output(["virsh", "list", "--state-running", "--name"], universal_newlines=True).strip() return [] if not as_string else as_string.split("\n")
# Evaluate command-line arguments:
parser = OptionParser(version="%prog 1.0")
parser.add_option("-i", "--interval", type="float", dest="interval", default=1, help="Interval to use for polling the VM state after sending the shutdown command. (default: %default)")
parser.add_option("-t", "--timeout", type="float", dest="timeout", default=30, help="Time to wait for all VMs to shut down. (default: %default)")
parser.add_option("-k", "--kill-on-timeout", action="store_true", dest="kill", default=False, help="Kill (power cut) all remaining VMs when the timeout is reached. " "Otherwise exit with error code 1. (default: %default)")
parser.add_option("-v", "--verbose", action="store_true", dest="verbose", default=False, help="Print verbose status output. (default: %default)")
parser.add_option("-z", "--zenity", action="store_true", dest="zenity", default=False, help="Print progress lines for 'zenity --progress' GUI progress dialog. (default: %default)")
(options, args) = parser.parse_args()
# List all running VMs:
running_vms = list_running_vms()
# Print summary of what will happen:
print("Shutting down all running VMs (currently {}) within {} seconds. {} remaining VMs.".format( len(running_vms), options.timeout, "Kill all" if options.kill else "Do not kill any"))
# Send shutdown command ("power-button-pressed" event) to all running VMs:
any_errors = False
if options.zenity: print("# Sending shutdown signals...", flush=True)
for vm in running_vms: if options.verbose: ok = subprocess.call(["virsh", "shutdown", vm]) else: ok = subprocess.call(["virsh", "shutdown", vm], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL) if ok != 0: print("Error trying to shut down VM '{}' (code {})!".format(vm, ok)) any_errors = True
# Don't start waiting if there was any error sending the shutdown command, exit with error:
if any_errors: print("ERROR: could not successfully send all shutdown commands!") exit(3)
# Wait for all VMs to shut down, but at most MAX_WAIT seconds. Poll every INTERVAL seconds::
t0 = time.time()
while running_vms: num_of_vms = len(running_vms) t = time.time() - t0 if options.zenity: print("# Waiting for {} VM{} to shut down... ({} seconds left)".format( num_of_vms, "" if num_of_vms == 1 else "s", int(options.timeout - t)), flush=True) print(int(100 * t/options.timeout) if t < options.timeout else 99, flush=True) if options.verbose or t > options.timeout: print("\n[{:5.1f}s] Still waiting for {} VMs to shut down:".format(t, num_of_vms)) print(" > " + "\n > ".join(running_vms)) if t > options.timeout: if options.kill: print("\nTimeout of {} seconds reached! Killing all remaining VMs now!".format(options.timeout)) if options.zenity: print("# Timeout reached! Have to kill the remaining {}.".format( "VM" if num_of_vms == 1 else "{} VMs".format(num_of_vms)), flush=True) for vm in running_vms: if options.verbose: ok = subprocess.call(["virsh", "destroy", vm]) else: ok = subprocess.call(["virsh", "destroy", vm], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL) if ok != 0: if options.verbose: print("Error trying to forcibly kill VM '{}' (code {})!".format(vm, ok)) any_errors = True if any_errors: print("ERROR: could not successfully send all destroy commands!") exit(3) else: print("ERROR: Timeout of {} seconds reached!".format(options.timeout)) exit(1) break time.sleep(options.interval) running_vms = list_running_vms()
print("#" if options.zenity else "" + " All VMs were shut down successfully.", flush=True)
if options.zenity: print(100, flush=True)
exit(0)shutdown-dialog-listener (in Bash, the Unity shutdown/logout watchdog):
#!/bin/bash
DISPLAY=:0
dbus-monitor --session "interface='com.canonical.Unity.Session'" | \ while read LINE;do \ if grep -qi 'reboot\|shutdown\|logout' <<< "$LINE" ;then \ VAR="$(virsh list --state-running --name)" if [ $(wc -w <<<$VAR) -gt 0 ]; then qdbus com.canonical.Unity /org/gnome/SessionManager/EndSessionDialog \ org.gnome.SessionManager.EndSessionDialog.Close vm-terminator fi fi ;doneAll three scripts are directly callable, the core script shutdown-all-vms even has a nice command-line help:
$ shutdown-all-vms --help
Usage: shutdown-all-vms [options]
Options: --version show program's version number and exit -h, --help show this help message and exit -i INTERVAL, --interval=INTERVAL Interval to use for polling the VM state after sending the shutdown command. (default: 1) -t TIMEOUT, --timeout=TIMEOUT Time to wait for all VMs to shut down. (default: 30) -k, --kill-on-timeout Kill (power cut) all remaining VMs when the timeout is reached. Otherwise exit with error code 1. (default: False) -v, --verbose Print verbose status output. (default: False) -z, --zenity Print progress lines for 'zenity --progress' GUI progress dialog. (default: False)Additionally, you may place shutdown-dialog-listener into your user account's startup applications.
Below is a small script that should be run as autostart entry or manually (if user prefers so). The basic idea is this: keep polling dbus session bus, and if we get reboot, or shutdown, or logout, then we can check if QEMU is running; if it is, kill the shutdown dialog, run the command to shutdown the VMs, and then call dbus to shutdown, or even call separate script with script-name.sh &
The example I have below was tested with firefox just for the sake of example (since I do not have QEMU), but it can be easily adapted. Comments included for guidance
#!/bin/bash
# You will need the DISPLAY variable, if you
# are running the script as an autostart entry
# DISPLAY=:0
dbus-monitor --session "interface='com.canonical.Unity.Session'" | \ while read LINE;do \ if grep -qi 'reboot\|shutdown\|logout' <<< "$LINE" ;then \ # This part could be either pgrep , or # VAR="$(virsh list --state-running --name)" # And then you can test whether or not variable is empty to see # if there are running processes PID="$(pgrep firefox)" if [ ! -z $PID ]; then # This is where you can take action # For instance the qdbus lengthy command closes the End Session dialog # which effectively prevents user from clicking shutdown # You can append another command, such as # virsh shutdown VMNAME or run an external script that does it. # Since this script is constantly polling dbus-monitor, we need to avoid # it's better to call external , in my opinion. notify-send "GOTCHA $PID"; qdbus com.canonical.Unity /org/gnome/SessionManager/EndSessionDialog \ org.gnome.SessionManager.EndSessionDialog.Close # After the action part is done, one could call # dbus to shutdown # qdbus com.canonical.Unity /com/canonical/Unity/Session com.canonical.Unity.Session.Shutdown fi fi ;done
