Using systemd --user to run fetchmail

Using systemd --user to run fetchmail
	Fetchmail from Google's Gmail

Fetchmail usually runs either as a single system wide daemon, or it's started by a user's cron job. But as you can see, the above fetchmail uses IMAP4's IDLE feature. So it has to keep a connection to the server open. Fetchmail can do this for only one connection at a time.

To me, that is enough, but I want my personal fetchmail instance to always run, not merely when I'm logged in. Luckily, systemd has a user feature that does exactly that.

Procedure 8. Running Fetchmail from Systemd

Enable lingering
We want that fetchmail to start at boot, not merely when I log in. Systemd calls it lingering (see also here), and we have to enable it as root (merely once) for the user:
sudo loginctl enable-linger apprentice
Enabling Sudo to call Systemctl
Systemctl talks to DBus. When calling systemctl through sudo for another user, there may be a bit of a problem because XDG_RUNTIME_DIR is not set properly. We can easily solve this in ~/.bashrc:
```
<snip>	    
export XDG_RUNTIME_DIR="/run/user/$(id -u)"
	  
```
Now when root sudos -s to become apprentice, it won't get
Failed to connect to bus: No such file or directory
<title> Config </title> Create a systemd unit in ~cpp/.config/systemd/user/fetchmail.service:
```
[Unit]
Description="Fetchmail Program"

[Service]
Environment="XDG_RUNTIME_DIR=/run/user/%U"
Environment="HOME=%h"
ExecStart=/usr/bin/fetchmail
Restart=always
Type=simple
# PIDFile Not needed
#PIDFile="%h/.fetchmail.pid"

[Install]
WantedBy=default.target
	  
```
Also check the config file for errors:
systemd-analyze verify ~cpp/.config/systemd/user/fetchmail.service systemd validate ~cpp/.config/systemd/user/fetchmail.service

Enable the service

Shown here is how to do it from the root account. But the user can also do it himself. XDG_RUNTIME_DIR here still has to be set from the command line because sudo doesn't use Bash:

sudo -u apprentice XDG_RUNTIME_DIR=/run/user/$(id -g apprentice) systemctl --user enable fetchmail

	Note
	This command creates a further structure under `~/.config/systemd/user`. If the WantedBy line in the unit file changes, that structure would chage as well, and this command has to be re-run. A daemon-reload is not enough.

Starting the service

apprentice@host:~$ systemctl --user start fetchmail

After this, fetchmail will run for the user as soon as the system is booted.


Fetchmail from Google's Gmail		Building Vera++ on Debian Stretch