Systemctl Commands Guide
Systemctl: Essential Linux Service Management
The systemctl command is the primary tool for controlling the systemd system and service manager in modern Linux distributions. It allows administrators to manage services, units, targets, and system states efficiently. Understanding systemctl is crucial for effective Linux system administration, enabling you to control how applications and system processes run.
Core Systemctl Operations
Here are some of the most common systemctl commands for managing services:
# To see running processes:
systemctl
# To check the status of a service:
systemctl status foo.service
# To start/restart/stop a service:
systemctl start/restart/stop foo.service
# To reload a service's configuration:
systemctl reload foo.service
# To edit a service's configuration:
systemctl edit foo.service
# To reload systemd manager configuration:
systemctl daemon-reload
# To enable a service to startup on boot:
systemctl enable foo.service
# To disable a service to startup on boot:
systemctl disable foo.service
# To start/restart/stop per-user service:
systemctl --user start/restart/stop emacs.service
Listing and Filtering Units
systemctl provides powerful ways to list and filter various types of units on your system:
# To see all active units, add --all for everything:
systemctl list-units
# To see all service units:
systemctl list-units -at service
# To see filtered units (all running service):
systemctl list-units -t service --state running
# To see all service files, see which are enabled or disabled:
systemctl list-unit-files -at service
# To list all units with specific status, inactive, active, enabled, running, exited:
systemctl list-units --all --state=inactive
# To use systemctl to list all unit files:
systemctl list-unit-files
Working with System Logs (Journalctl)
While systemctl manages services, journalctl is used to view logs generated by systemd and services:
# To see log items from the most recent boot:
journalctl -b
# To to see only kernal messages, add -b for at the most recent boot:
journalctl -k
# To get the log entries for a service since boot:
journalctl -b -u foo.service
Advanced Systemctl Features
Explore more advanced functionalities for deeper system insights:
# To list the dependencies of a service:
# when no service name is specified, lists the dependencies of default.target
# add -all to expand dependencies recursively
systemctl list-dependencies foo.service
# To see low level details of a service settings on the system:
systemctl show foo.service
# To list currently loaded targets:
systemctl list-units --type=target
# To change current target:
systemctl isolate foo.target
# To change default target:
systemctl enable foo.target