Merge pull request #843 from Buzut/master

Update to add systemd daemon exemple

Author: ben

book/04-git-server/sections/git-daemon.asc

@@ -20,7 +20,40 @@ $ git daemon --reuseaddr --base-path=/srv/git/ /srv/git/
 If you're running a firewall, you'll also need to punch a hole in it at port 9418 on the box you're setting this up on.
 
 You can daemonize this process a number of ways, depending on the operating system you're running.
-On an Ubuntu machine, you can use an Upstart script.
+
+Since `systemd` is the most common init system among modern Linux distributions, you can use it for that purpose.
+Simply place a file in `/etc/systemd/system/git-daemon.service` with these contents:
+
+[source,console]
+----
+[Unit]
+Description=Start Git Daemon
+
+[Service]
+ExecStart=git daemon --reuseaddr --base-path=/srv/git/ /srv/git/
+
+Restart=always
+RestartSec=500ms
+
+StandardOutput=syslog
+StandardError=syslog
+SyslogIdentifier=git-daemon
+
+User=git
+Group=git
+
+[Install]
+WantedBy=multi-user.target
+----
+
+You might have noticed that Git daemon is started here with `git` as both group and user. 
+
+Modify it to fit your needs and make sure provided user exists on the system.
+
+Finally, you'll run `systemctl enable git-daemon` to automatically start the service on boot, and the usual service commands like `service start` and `service stop` are instantly available.
+
+Until LTS 14.04, Ubuntu used upstart service unit configuration. 
+Therefore, on Ubuntu <= 14.04 you can use an Upstart script.
 So, in the following file
 
 [source,console]