Posts tagged systemd
Use systemd timers to make PostgreSQL backups
- 27 July 2023
Systemd timers are a great way to replace cron jobs. They are more flexible and can have dependencies that can defined in easy statements instead of creating a script to check for the dependency. One of the use-cases is to use systemd timers to create PostgreSQL backups and remove old backups. In this example, we will create a backup of two databases, db1 and db2, and remove backups older than 10 days.
First step is to install PostgreSQL on the system. This example is for Debian or Ubuntu and uses the root user to connect to the database. It is recommended to create a user with limited privileges to connect to the database.
Use systemd timers to make MariaDB backups
- 23 July 2023
Systemd timers are a great way to replace cron jobs. They are more flexible and can have dependencies that can defined in easy statements instead of creating a script to check for the dependency. One of the use-cases is to use systemd timers to create MariaDB backups and remove old backups. In this example, we will create a backup of two databases, db1 and db2, and remove backups older than 10 days.
First step is to install MariaDB on the system. This example is for Debian or Ubuntu and uses the root user to connect to the database. It is recommended to create a user with limited privileges to connect to the database.
Manage multiple systemd service instances
- 17 July 2023
With systemd you can manage services like in post Environment variables set by systemd, but managing multiple instances of the same service is not so easy. For example, you have a service that runs a web server, and you want to run multiple instances of that service, each with different configuration. You can do that by creating multiple service files, but that is not very elegant. You can also use systemd templating, but that is not very flexible. The best way to do this is to use systemd instances.
For the example, we will create a service that runs a Python script. The script will print the value of an environment variable. The name of the environment variable will be the name of the instance. The script will be called env_variables.py and will be located in /usr/local/bin/. The service will be called env_variables@.service and will be located in /etc/systemd/system/. So let’s copy the script from the previous post as it can print the value of an environment variable to the standard output.
Environment variables set by systemd
- 02 July 2019
Applications sometimes need environment variables to be set for triggering certain behavior like giving debug output or routing traffic via a HTTP-proxy for example. A common way is to modify the start-stop script, but with systemd on most Linux systems, like Debian and Red Hat based distributions, this can also be directly set within the unit file and you don’t have to export the variables anymore.
Let’s start with a Python script to read and print the environment variables set by the environment to see how this works. The Python script below that we run via systemd checks if environment variable VAR1 has been set and will generate different output based on that.