systemd is a suite of system components for Linux. Its central component is a system and service manager that runs as PID 1, coordinates the boot process and manages services throughout their lifecycle.
The software uses a dependency-based approach to starting and stopping system components. Services can be activated on demand, started in parallel and monitored through Linux control groups. Administrators define their behaviour using unit files, which describe services, sockets, timers, mount points and other managed resources.
Beyond service management, systemd includes tools for logging, device management, networking, user sessions and system configuration. The particular components installed and enabled depend on the Linux distribution.
This is free and open source software.
Key Features
- Manage system services using systemctl, including starting, stopping, enabling, disabling and inspecting units.
- Support eleven unit types: service, socket, device, mount, automount, swap, target, path, timer, slice and scope.
- Manage dependencies and ordering between units using declarative configuration files.
- Start independent services in parallel to reduce unnecessary delays during boot.
- Activate services on demand through socket activation, D-Bus activation and other mechanisms.
- Schedule recurring and one-off tasks using timer units with calendar-based or monotonic time expressions.
- Create transient services and timers using systemd-run without maintaining permanent unit files.
- Monitor services and restart failed processes according to configurable policies.
- Manage CPU, memory, I/O and process limits through Linux control groups.
- Apply service security restrictions, including filesystem isolation, capability limits, system call filtering and restricted access to devices.
- Collect and query structured system logs through systemd-journald and journalctl.
- Analyse boot performance, unit dependencies and service security settings using systemd-analyze.
- Support separate system-wide and per-user service managers.
- Manage device events and permissions through systemd-udevd.
- Provide optional network configuration, DNS resolution and time synchronisation through systemd-networkd, systemd-resolved and systemd-timesyncd.
- Track user logins, sessions and seats through systemd-logind.
- Manage temporary files, runtime directories, system users and groups through systemd-tmpfiles and systemd-sysusers.
- Support filesystem mount and automount management, including activation on access.
- Offer service watchdog integration, readiness notifications and configurable timeouts.
- Provide optional components for boot management, system credentials, home directories and out-of-memory handling.
- Support compatibility with traditional SysV init scripts through appropriate integration mechanisms.
Website: systemd.io
Support:
Developer: systemd development team
License: GNU Lesser General Public License v2.1 (main code); GNU General Public License v2.0 (selected udev components)
systemd is written in C. Learn C with our recommended free books and free tutorials.
Related Software
| Alternatives to cron | |
|---|---|
| cronie | Modern day version of cron and associated tools |
| fcron | Designed for systems which are not continuously running or regularly |
| Cronicle | Multi-server task scheduler and runner |
| systemd | Suite of basic building blocks for a Linux system |
| Supercronic | Crontab-compatible job runner designed for container environments |
| Ofelia | Low-footprint job scheduler for Docker environments |
| Dkron | Distributed job scheduling system for cloud native environments |
| mcron | 100% compatible replacement for Vixie cron |
| Dagu | Lightweight workflow orchestration engine |
| anacron | Designed for systems which are not continuously running |
| Jobber | Run commands to a schedule |
| bcron | Designed with secure operations in mind |
| Chadburn | Modern job scheduler for Docker environments |
| runcron | Minimal cron alternative for automated and container-friendly environments |
Read our verdict in the software roundup.
 Explore our carefully curated directory of recommended free and open source software, covering every major software category.The directory forms part of our extensive collection of articles for Linux enthusiasts. It includes hundreds of detailed reviews, together with free and open source alternatives to proprietary software from companies such as Google, Microsoft, Apple, Adobe, IBM, Cisco, Oracle, and Autodesk. LinuxLinks also covers interesting projects worth exploring, Linux-compatible hardware, free programming books and tutorials, and much more. Know a useful free and open source Linux application that we haven’t covered? Tell us about it using our submission form. |
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