Testing inhibitor locks

configure_logind.sh

#!/bin/bash

cat <<EOF > /etc/systemd/system/inhibit.service
[Unit]
Description=heh
After=network.target

[Service]
Type=simple

ExecStart=/home/ubuntu/inhibit
KillMode=none

[Install]
WantedBy=multi-user.target
EOF

systemctl daemon-reload
systemctl start inhibit.service

sed -i 's/#InhibitDelayMaxSec=5/InhibitDelayMaxSec=600/g' /etc/systemd/logind.conf
apt purge unattended-upgrades -y
systemctl reload systemd-logind

inhibit.go

// thanks to https://trstringer.com/systemd-inhibitor-locks/

package main

import (
	"fmt"
	"os"

	"github.com/godbus/dbus/v5"
)

func main() {
	fmt.Println("Starting dbus example")

	// Get a handle on the system bus. There are two types
	// of buses: system and session. The system bus is for
	// handling system-wide operations (like in this case,
	// shutdown). The session bus is a per-user bus.
	conn, err := dbus.SystemBus()
	if err != nil {
		fmt.Printf("error getting system bus: %v\n", err)
		os.Exit(1)
	}
	defer conn.Close()

	// Call the Inhibit method so that this process register
	// an inhibitor lock. This returns a file descriptor so
	// that after a shutdown signal this process can signal
	// back to systemd that it is complete by closing the
	// file descriptor.
	//
	// The parameters that are passed to Inhibit dictate the
	// state change. In this case, that is "shutdown". The
	// mode can either be "delay" or "block". Delay will halt
	// the state change for the InhibitDelayMaxSec setting,
	// which defaults to 5 seconds. Block will indefinitely
	// block the operation and should be used with caution.
	var fd int
	err = conn.Object(
		"org.freedesktop.login1",
		dbus.ObjectPath("/org/freedesktop/login1"),
	).Call(
		"org.freedesktop.login1.Manager.Inhibit", // Method
		0,                                        // Flags
		"shutdown",                               // What
		"Inhibitor Test",                         // Who
		"Testing systemd inhibitors from Go",     // Why
		"delay",                                  // Mode
	).Store(&fd)
	if err != nil {
		fmt.Printf("error storing file descriptor: %v\n", err)
		os.Exit(1)
	}
	fmt.Printf("Inhibitor file descriptor: %d\n", fd)

	// Call AddMatch so that this process will be notified for
	// the PrepareForShutdown signal. This will allow us to do
	// custom logic when the machine is getting ready to shutdown.
	err = conn.AddMatchSignal(
		dbus.WithMatchInterface("org.freedesktop.login1.Manager"),
		dbus.WithMatchObjectPath("/org/freedesktop/login1"),
		dbus.WithMatchMember("PrepareForShutdown"),
	)
	if err != nil {
		fmt.Printf("error adding match signal: %v\n", err)
		os.Exit(1)
	}

	fmt.Println("Beginning to sleep forever")

	select {}
}