This is the older style of working with services is to use the services and chkconfig commands, if possible you should use the newer systemctl commands below
| chkconfig | chkconfig <service> --list chkconfig on <service> chkconfig off <service> chkconfig --levels 234 <service> on chkconfig --levels 234 <service> off chkconfig --add <service> chkconfig --remove <service> |
| service | service <service> status service <service> start service <service> stop service <service> restart service <service> --status-all |
This is the newer style of working with services and replaces the old service and chkconfig commands
| Directory stucture and service files | /etc/systemd # global config dir /usr/lib/systemd/system # unit/configuration files /etc/systemd/systems # target directories with links to service (unit) files ls -l /usr/lib/systemd/system/ |grep target # list targets ls -l /usr/lib/systemd/system/ |grep service # list service (also have mount, automount, path, socket, timer, slice) |
| Version | systemctl --version # version |
| Boot time information | systemd-analyze # boot time systemd-analyze blame # boot time for each service (unit) systemd-analyze critical-chain # critical chain boot timings systemd-analyze critical-chain sshd.service # specific service (unit) boot timings |
| Dependancies | systemctl list-dependencies # List of service (unit) dependancies (text graphics) systemctl list-dependencies sshd # dependancies of a specific service (unit) systemctl list-dependencies graphical.target | grep target # dependancies of a specific target |
| Systemd handles the system event log through Journald | journalctl # display system events log journalctl /sbin/crond # display events for crond journalctl /sbin/sshd # display events for sshd (lots more) journalctl -u chronyd # display events for a specific service journalctl -b # display events since last reboot journalctl -k # display kernel events journalctl --since=today # display events since for today journalctl -p err # display events with a priority (0/emerg upto 7/debug) journalctl -f # tail events journalctl --list-boots # list recent reboots journalctl --disk-usage # display disk usage by journalctl |
| Systemd organizes processes in control groups | systemd-cgls # system control groups systemd-cgtop # system control group top (monitoring/performance) systemctl list-units -all # Detailed list of all services (units) systemctl list-units -all --state=[inactive|active] # Same as above but with specific state systemctl list-units -all --type=[service|target|mount|device] # Same as above but type is a specific service, device, target or mount, etc systemctl list-unit-files # List all services (units) systemctl list-units --type=target # List all types (ideal for runlevels) systemctl --failed # List all failed services (units) systemctl cat sshd # List service unit file (how it starts, kill comand, etc) systemctl edit sshd --full # Edit unit file above systemctl show httpd # show a service properties (i.e restart, timeouts, controlPID) systemctl kill httpd # kill a service systemctl mask httpd # Stops a service automatically or manually being started (links to dev/null) systemctl unmask httpd # unmasks a service (see above line) systemctl enable sshd # Enable a service (adds symlink to service from /etc/systemd/system to /usr/lib/systemd/system) systemctl disable sshd # Disable a service (removes symlink from /usr/lib/systemd/system) systemctl start sshd # Start a service systemctl stop sshd # Stop a service systemctl status sshd # get status of service systemctl restart sshd # Restart a service systemctl reload sshd # Reload a service systemctl reload-or-restart # Service will either be reloaded or restarted systemctl is-enabled sshd # is service started at boot (chkconfig) systemctl is-active sshd # is service running systemctl is-failed sshd # has service failed systemctl daemon-reload # reload a service after a change |
| Service state | enabled # explicitly installed static # installed as dependency (cannot be enable or disable manually) disabled # not installed |
| target and Runlevels | who -r # Get current runlevel runlevel # Get current runlevel systemctl list-units --type=target # Identify runlevel types systemctl rescue # Move to Maintenance mode systemctl isolate runlevel3.target # Move to runlevel 3 systemctl isolate multi-user.target # Move to runlevel 3 (multi-user) systemctl isolate graphical.target # Move to runlevel 5 (graphical) systemctl get-default # Get default runlevel (/etc/systemd/system/default.target which is a symlink to a target) systemctl set-default graphical.target # Set default runlevel systemctl poweroff # Power off server systemctl reboot # Reboot server systemctl suspend # Suspend server systemctl hibernate # Hibernate server |
| Traditional runLevelv New Target Name | Runlevel 0 | runlevel0.target -> poweroff.target Runlevel 1 | runlevel1.target -> rescue.target Runlevel 2 | runlevel2.target -> multi-user.target Runlevel 3 | runlevel3.target -> multi-user.target Runlevel 4 | runlevel4.target -> multi-user.target Runlevel 5 | runlevel5.target -> graphical.target Runlevel 6 | runlevel6.target -> reboot.target |