Link
  1. Systemd
    1. Listing services
    2. Managing Targets (similiar to Runlevels in SysV)
    3. Managing Services
    4. Managing autostart of services
    5. Masking services
    6. Restart Systemd
    7. Diagnosing problems with a service
  2. Service Management
  3. Runlevels

Systemd

Listing services

systemctl : list running services
systemctl --failed : list failed services

Managing Targets (similiar to Runlevels in SysV)

systemctl get-default : (dispays the default target for the system)
systemctl set-default <target-name> : (set the default target for the system)

Managing Services

systemctl <start|stop|restart> <service> : start, stop, or restart a service
systemctl reload <service> : request service to reload its configuration
systemctl status <service> : show current status of service

Managing autostart of services

systemctl is-enabled <service> : show whether a service is enabled on boot or not
systemctl is-active <service> : show whether a service is currently running (active)
systemctl <enable|disable> <service> : enable/disable a service on boot

Masking services

systemctl mask <service> : mask a service (makes it hard to start by mistake)
systemctl unmask <service> : unmask a service

Restart Systemd

systemctl daemon-reload

Diagnosing problems with a service

journalctl -xe : loads the last 1000 logged lines into a pager, jumping to the end
journalctl -f : follow log messages as they come in
journalctl -f -t sshd follow logs for a particular service, in this case “sshd”
journalctl -p err -S yesterday : show all items logged as errors since yesterday
tail -f /var/log/messages : If journalctl is not available, most services on the system log to /var/log/messages
tail -f /var/log/secure : Or, if the service is privileged, it may log sensitive data to /var/log/secure

Service Management

SysVInit Systemd Notes
service <service> <start,stop,restart,reload>
Example: service sshd start
systemctl <start,stop,restart,reload> <service>
Example: systemctl start sshd
Used to control a service (not reboot persistent)
service <service> condrestart systemctl condrestart <service> Restarts a service already running
service <service> status systemctl status <service> Is the service running?
ls /etc/rc.d/init.d/ systemctl list-unit-files --type=service
ls/ /lib/systemd/system/*service
ls /etc/systemd/system/*service
Used to list services that can be started or stopped with scripts
chkconfig <service> <on,off> systemctl <enable,disable> <myservice> Turn service on, start at next boot or other trigger
chkconfig <service> systemctl is-enabled <service> Check whether a service is configured to start on boot or not
chkconfig --list systemctl list-unit-files --type=service
ls /etc/systemd/system/*.service
List all services and runlevels and what they are configured for
chkconfig <service> --list ls /etc/systemd/system/*wants/<service>.service List all runlevels for which this service is configured for
chkconfig <service> --add systemctl daemon-reload Used when you create a new service file or modify any configuration

Runlevels

SysVInit Systemd Notes
0 poweroff.target halt the system
1 rescue.target single-user mode
2 multi-user.target multi-user.target without networking
3 multi-user.target multi-user.target with networking
4 multi-user.target user-configurable
5 graphical.target multi-user.target with gui
6 reboot.target reboot the system

Resources and More

Init System Debate - Debian wiki
Comparison of Init Systems - Gentoo wiki