SystemD survival guide

This is a short guide I've wrote to start working with systemd after its 'stampede' entrance in Linux distrubitions.

Note that services are now kind of units (the default unit type). There are also socket, device, and other types of unit.

For simplicity of understanding I usually will be talking about service while really may be any kind of unit

The usual service command should still work as usual (I recommend to keep it using as portable tool, in hope that some time in future distributions rethink their choice):

 service <service> start
 service <service> stop
 service <service> reload
 service <service> restart
 service <service> status

For reference, the systemd command (super-command-tool-manager-of-all) to achieve the same (which is really called when you type any of the above commands):

systemctl start <service>
systemctl stop <service>
systemctl reload <service>
systemctl restart <service>
systemctl status <service>

In order to enable disable automatic or not-so-automatic startup of services:

systemctl disable <service>
systemctl enable <service>
systemctl mask <service>
systemctl unmask <service>

Mask/Unmask totally disable/enable the service no only at boot as on call too.

 systemctl 
 systemctl list-unit-files
 systemctl list-dependencies

Well, runlevels had gone, now we have 'targets' which really are the same with another name. There are symbolic links from runlevel to to the equivalent target to ease their use.

Really, a target is a grouping of units which must be started to achieve that

 systemctl enable multi-user.target --force

 systemctl isolate <target>

These are called specials. Because systemd not only replaced init, it also supply some other non-init features which may interact/interfer with your normal unix understanding. This is a list which I'm now currently learning how to deal with:

• cron
• dhcp

  • inet superserver (inetd, xinetd …)
  • system logging
  • automount
  • resolve (both NSS and DNS)
  • login
  • sysctl?

  Advanced

Seems /etc/systemd/system.conf configure the whole systemd init, while the rest of files under the directory configure services provided by systemd.