Schedule jobs with systemd-timer

Since I had trouble using cron, and crontab, in the past I decided to use systemd instead. You are also able to monitor them in a better way than in cron.

1st Example: CrowdSec hub update in docker container

Hub updates in the CrowdSec container must be handled manually because there is no (systemd) services installed which can handle that.
At first I created a basic shell script, for instance, called crowdsec-hub-update. Yes, without .sh file extension.

#!/usr/bin/bash
docker exec crowdsec cscli hub update
docker exec crowdsec cscli hub upgrade

Hint: Create this file in /usr/local/bin to make it globally available.

Configuration

Create a timer-file in /etc/systemd/system called crowdsec-hub-update.timer.

[Unit]
Description="CrowdSec hub update everyday at every hour."
[Timer]
Unit=crowdsec-hub-update.service
OnBootSec=1min
OnCalendar=*-*-* *:00:00 # DOW YYYY-MM-DD HH:MM:SS
[Install]
WantedBy=timers.target

value	description
Unit=	which unit (or service-file) this timer triggers
OnBootSec=	waiting after boot before 1st executing, comment or delete this line if you just want to make use of OnCalendar entry
OnCalendar=	defines a exact time, like in cron, when the unit is executed next

After that create the corresponding unit in the same folder called crowdsec-hub-update.service.

[Unit]
Description="Update and upgrade CrowdSec Hub."
Requires=crowdsec-hub-update.timer
[Service]
Type=simple
ExecStart=/path/to/crowdsec-hub-update
User=root

value	description
Requires=	On which object does it depend
ExecStart=	path to the script, this is handy if you have more than one command
User=	which user executes the command

Usage

systemctl enable crowdsec-hub-update.timer
systemctl ( start | stop ) crowdsec-hub-update.timer

When you start the timer the service will be executed once!

2nd Example: Add MACVLAN interface for AdGuard Home container

I want my AdGuard Home container to have its own IP address, but this setting, however, gets lost on every reboot. So… I created a bash script named add-macvlan-interface.

#!/bin/bash
ip link add mac0 link eth0 type macvlan mode bridge
ip addr add 192.168.0.252/30 dev mac0
ifconfig mac0 up

This creates a new device called mac0 linked as bridge to eth0 with an gateway IP set. When the docker container boots, it is a member of this network, the network interface will obtain the first ip which is .253.

Configuration tasks at boot

Create a service-file in /etc/systemd/system named, e.g., add-mac-vlan-int.service.

[Unit]
Description="Add Docker MacVLAN interface for AdGuard Home."
Wants=network.target
After=syslog.target network-online.target
[Service]
Type=simple
ExecStart=/home/dietpi/git/add-macvlan-interface
Restart=on-failure
RestartSec=10
KillMode=process
User=root
[Install]
WantedBy=multi-user.target

It is the same process as creating recurring tasks, but without a timer-file. This unit will start at boot (when you enable it) after the network got initialized.

Usage

systemctl enable add-macvlan-int.service

You can add --now if you want to also start the service with enabling.

Troubleshooting

systemctl status crowdsec-hub-update.timer
systemctl status crowdsec-hub-update.service

jounralctl -u crowdsec-hub-update.service