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


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


SysVInit Systemd Notes
0 halt the system
1 single-user mode
2 without networking
3 with networking
4 user-configurable
5 with gui
6 reboot the system

Resources and More

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