Is it possible to set Ubuntu a way that it does not shutdown before a script is finished?

I use a script to do incremental backups of a btrfs partition from one disk to another.

The script is started by cron.weekly at random time of a day.

If I shut down the system while the script is running, I am getting into trouble with old backups removed and new not created.

Is there a way to setup the system to wait till the script is finished?

I am using Ubuntu 16.04 with systemd.

Solution 1:

For Ubuntu 16.04+ using systemd (the default).

systemd-inhibit --why="Wait for this script to finish" bash script.sh

===

Test:

$ systemctl poweroff
Operation inhibited by "bash script.sh" (PID 23912 "systemd-inhibit", user rinzwind),
reason is "Wait for this script to finish".
Please retry operation after closing inhibitors and logging out other users.

===

There are 7 locks:

• sleep inhibits system suspend and hibernation requested by (unprivileged) users
• shutdown inhibits high-level system power-off and reboot requested by (unprivileged) users
• idle inhibits that the system goes into idle mode, possibly resulting in automatic system suspend or shutdown depending on configuration.
• handle-power-key inhibits the low-level (i.e. logind-internal) handling of the system power hardware key, allowing (possibly unprivileged) external code to handle the event instead.
• handle-suspend-key inhibits the low-level handling of the system hardware suspend key.
• handle-hibernate-key inhibits the low-level handling of the system hardware hibernate key.
• handle-lid-switch inhibits the low-level handling of the systemd hardware lid switch.

You probably also want to prevent suspend, idle and hibernate.

Example using "package manager":

fd = Inhibit("shutdown:idle", "Package Manager", "Upgrade in progress...", "block");
/* ...
      do your work
                 ... */
close(fd);

Similar to this you can code your version and add a "shutdown" at the end of this script (or add a way to determine a shutdown needs to be the next action).

Solution 2:

In BackInTime I'm using couple different DBus methods to work on all major DEs. Only downside is this won't work for root because root has no dbus.SessionBus.

#!/usr/bin/env python3
import sys
import dbus
from time import sleep

INHIBIT_LOGGING_OUT = 1
INHIBIT_USER_SWITCHING = 2
INHIBIT_SUSPENDING = 4
INHIBIT_IDLE = 8

INHIBIT_DBUS = (
               {'service':      'org.gnome.SessionManager',
                'objectPath':   '/org/gnome/SessionManager',
                'methodSet':    'Inhibit',
                'methodUnSet':  'Uninhibit',
                'interface':    'org.gnome.SessionManager',
                'arguments':    (0, 1, 2, 3)
               },
               {'service':      'org.mate.SessionManager',
                'objectPath':   '/org/mate/SessionManager',
                'methodSet':    'Inhibit',
                'methodUnSet':  'Uninhibit',
                'interface':    'org.mate.SessionManager',
                'arguments':    (0, 1, 2, 3)
               },
               {'service':      'org.freedesktop.PowerManagement',
                'objectPath':   '/org/freedesktop/PowerManagement/Inhibit',
                'methodSet':    'Inhibit',
                'methodUnSet':  'UnInhibit',
                'interface':    'org.freedesktop.PowerManagement.Inhibit',
                'arguments':    (0, 2)
               })

def inhibitSuspend(app_id = sys.argv[0],
                    toplevel_xid = None,
                    reason = 'take snapshot',
                    flags = INHIBIT_SUSPENDING | INHIBIT_IDLE):
    """
    Prevent machine to go to suspend or hibernate.
    Returns the inhibit cookie which is used to end the inhibitor.
    """
    if not app_id:
        app_id = 'backintime'
    if not toplevel_xid:
        toplevel_xid = 0

    for dbus_props in INHIBIT_DBUS:
        try:
            bus = dbus.SessionBus()
            interface = bus.get_object(dbus_props['service'], dbus_props['objectPath'])
            proxy = interface.get_dbus_method(dbus_props['methodSet'], dbus_props['interface'])
            cookie = proxy(*[(app_id, dbus.UInt32(toplevel_xid), reason, dbus.UInt32(flags))[i] for i in dbus_props['arguments']])
            print('Inhibit Suspend started. Reason: %s' % reason)
            return (cookie, bus, dbus_props)
        except dbus.exceptions.DBusException:
            pass
    print('Inhibit Suspend failed.')

def unInhibitSuspend(cookie, bus, dbus_props):
    """
    Release inhibit.
    """
    assert isinstance(cookie, int), 'cookie is not int type: %s' % cookie
    assert isinstance(bus, dbus.bus.BusConnection), 'bus is not dbus.bus.BusConnection type: %s' % bus
    assert isinstance(dbus_props, dict), 'dbus_props is not dict type: %s' % dbus_props
    try:
        interface = bus.get_object(dbus_props['service'], dbus_props['objectPath'])
        proxy = interface.get_dbus_method(dbus_props['methodUnSet'], dbus_props['interface'])
        proxy(cookie)
        print('Release inhibit Suspend')
        return None
    except dbus.exceptions.DBusException:
        print('Release inhibit Suspend failed.')
        return (cookie, bus, dbus_props)

if __name__ == '__main__':
    cookie, bus, dbus_props = inhibitSuspend()
    print('do something here')
    sleep(10)
    unInhibitSuspend(cookie, bus, dbus_props)