Systemd
Introduction
Systemd is a system and service manager for Linux. For many Linux distributions it replaced the existing SysV init system, modernizing how services are started and monitored.
Some basics about systemd:
- Author: Lennart Poettering
- First release: 2010
- First adopter: Fedora Linux
- Common usage by major Linux distributions: 2015
Learn more: What is systemd?
Systemd units
To monitor and manage services on a system using systemd, unit files are used. These text-based files define what to run or do, relevant conditions, and any applicable dependencies.
Learn more:
Commands
Systemd has a range of commands to interact with the systemd components. Have a look at the systemd commands page to see them all and learn about their purpose.
Relevant cheat sheets:
Hardening profiles for systemd
Hardening profiles for systemd that can be used to secure your applications.
Run0: introduction and usage
Learn the goal and purpose of run0 and how to use it for elevating privileges.
Systemd commands
All commands related to systemd in one overview. Learn about their purpose and when to use them.
Systemd features to secure units and services
Learn more about systemd features that help in securing units and services.
Systemd settings
Units in systemd have their own set of configuration settings. This overview shows the availability and their purpose.
Systemd syscall filtering
Learn more about the system calls (syscalls) that systemd may use in commands and unit files, such as with SystemCallFilter property.
Systemd timers
Learn about systemd timers, the unit type for scheduled tasks and how it differs from cron.
Systemd units and their purpose
Which systemd unit types are available and what is their goal? In this article we cover them and show some useful commands related to these units.
Troubleshooting a failed systemd unit (with examples)
Learn how to troubleshoot failed systemd units, examples, possible causes, and how to resolve them.
Frequently Asked Questions
What does 'systemctl daemon-reload' do?
When running 'systemctl daemon-reload', the systemd manager configuration is reloaded. It does this by running the generators that are helper scripts to create non-native systemd scripts. The dependency tree that links units in the right order is recreated and unit files containing their configuration are reloaded.
How to check if 'systemctl daemon-reload' is needed?
How to see which syscalls are part of a systemd syscall filter set?
What is the difference between systemctl disable and systemctl mask?
Using systemctl disable will no longer automatically start a service, while systemctl mask will administratively disable a service from running at all.
How to see only running services with systemctl?
How to disable the background color of run0
How to see memory usage of a service with systemctl?
How to see the time synchronization details with timedatectl?
How to see the dependencies of a systemd unit?
How to see all active systemd units of one type?
How to limit the disk usage of the systemd journal?
Define SystemMaxUse in /etc/systemd/journald.conf and restart systemd-journald.
What is a systemd unit?
Systemd units define resources, such as a service, path, socket, or timer. They are usually managed with the systemctl command.