Software/systemd/TipsAndTricks

Tips & Tricks

Also check out the Frequently Asked Questions!

Listing running services

$ systemctl
UNIT                                          LOAD   ACTIVE       SUB          JOB             DESCRIPTION
messagebus.service                            loaded active       running                      messagebus.service
basic.target                                  loaded active       active                       Basic System
sysinit.target                                loaded active       active                       Systemd Initialization
local-fs.target                               loaded active       active                       Local File Systems
swap.target                                   loaded active       active                       Swap
sockets.target                                loaded active       active                       Sockets
...

Showing runtime status

$ systemctl status udisks.service
udisks.service - udisks Disk Manager
          Loaded: loaded (/etc/systemd/system/multi-user.target.wants/../udisks.service)
          Active: active (running)
         Process: 999 (udisks-daemon)
          CGroup: name=systemd:/systemd-1/udisks.service
                  │
                  ├ 999 /usr/libexec/udisks-daemon
                  ├ 1018 udisks-daemon: polling /dev/sr0
                  └ 1132 /usr/libexec/udisks-daemon

cgroup tree

The tree tool is very handy to list the tree of control groups: 

$ tree -d /cgroup/systemd/ 
/cgroup/systemd/
├── systemd-1
│   ├── abrtd.service
│   ├── accounts-daemon.service
│   ├── acpid.service
...
│   ├── crond.service
│   ├── cups.service
│   ├── getty@.service
│   │   ├── tty1
│   │   ├── tty3
│   │   ├── tty4
│   │   ├── tty5
│   │   └── tty6
│   ├── haldaemon.service
│   ├── mdmonitor.service
│   ├── messagebus.service
...
│   ├── udisks.service
│   ├── upowerd.service
│   └── wpa_supplicant.service
└── user
    └── lennart
        ├── 1
        └── 2

38 directories

ps with cgroups

$ alias psc='ps xawf -eo pid,user,cgroup,args'
$ psc
  PID USER     CGROUP                              COMMAND
...
    1 root     name=systemd:/systemd-1             /bin/systemd systemd.log_target=kmsg systemd.log_level=debug selinux=0
  415 root     name=systemd:/systemd-1/sysinit.service /sbin/udevd -d
  928 root     name=systemd:/systemd-1/atd.service /usr/sbin/atd -f
  930 root     name=systemd:/systemd-1/ntpd.service /usr/sbin/ntpd -n
  932 root     name=systemd:/systemd-1/crond.service /usr/sbin/crond -n
  935 root     name=systemd:/systemd-1/auditd.service /sbin/auditd -n
  943 root     name=systemd:/systemd-1/auditd.service  \_ /sbin/audispd
  964 root     name=systemd:/systemd-1/auditd.service      \_ /usr/sbin/sedispatch
  937 root     name=systemd:/systemd-1/acpid.service /usr/sbin/acpid -f
  941 rpc      name=systemd:/systemd-1/rpcbind.service /sbin/rpcbind -f
  944 root     name=systemd:/systemd-1/rsyslog.service /sbin/rsyslogd -n -c 4
  947 root     name=systemd:/systemd-1/systemd-logger.service /lib/systemd/systemd-logger
  950 root     name=systemd:/systemd-1/cups.service /usr/sbin/cupsd -f
  955 dbus     name=systemd:/systemd-1/messagebus.service /bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation
  969 root     name=systemd:/systemd-1/getty@.service/tty6 /sbin/mingetty tty6
  970 root     name=systemd:/systemd-1/getty@.service/tty5 /sbin/mingetty tty5
  971 root     name=systemd:/systemd-1/getty@.service/tty1 /sbin/mingetty tty1
  973 root     name=systemd:/systemd-1/getty@.service/tty4 /sbin/mingetty tty4
  974 root     name=systemd:/user/lennart/2        login -- lennart     
 1824 lennart  name=systemd:/user/lennart/2         \_ -bash
  975 root     name=systemd:/systemd-1/getty@.service/tty3 /sbin/mingetty tty3
  988 root     name=systemd:/systemd-1/polkitd.service /usr/libexec/polkit-1/polkitd
  994 rtkit    name=systemd:/systemd-1/rtkit-daemon.service /usr/libexec/rtkit-daemon
...

Changing the Default Boot Target

$ ln -sf /lib/systemd/system/multi-user.target /etc/systemd/system/default.target

This line makes the multi user target (i.e. full system, but no graphical UI) the default target to boot into. This is kinda equivalent to setting runlevel 3 as the default runlevel on Fedora/sysvinit systems. 

$ ln -sf /lib/systemd/system/graphical.target /etc/systemd/system/default.target

This line makes the graphical target (i.e. full system, including graphical UI) the default target to boot into. Kinda equivalent to runlevel 5 on fedora/sysvinit systems. This is how things are shipped by default.

cgroup tree

$ systemd-cgls 
├     2 [kthreadd]
[...]
├ 29167 [flush-253:0]
├ user
│ └ lennart
│   ├ 39
│   │ ├ 29075 sshd: lennart [priv]
│   │ ├ 29079 sshd: lennart@pts/0
│   │ ├ 29080 -bash
│   │ └ 29168 systemd-cgls
│   └ 1
│     ├ 1141 login -- lennart
│     ├ 1532 -bash
│     ├ 1615 ssh-agent
│     └ 1641 gpg-agent --daemon --write-env-file
└ systemd-1
  ├ 1 /bin/systemd systemd.log_target=kmsg systemd.log_level=debug selinux=0
  ├ sshd@.service
  │ └ 4
  ├ prefdm.service
  │ └ 1272 /usr/sbin/gdm-binary -nodaemon
  ├ systemd-logger.service
  │ └ 1162 /lib/systemd/systemd-logger
  ├ getty@.service
  │ ├ tty3
  │ │ └ 1148 /sbin/mingetty tty3
  │ ├ tty2
  │ ├ tty4
  │ │ └ 1136 /sbin/mingetty tty4
  │ ├ tty5
  │ │ └ 1132 /sbin/mingetty tty5
  │ └ tty6
  │   └ 1125 /sbin/mingetty tty6
  ├ mdmonitor.service
  │ └ 1194 mdadm --monitor --scan -f --pid-file=/var/run/mdadm/mdadm.pid
  ├ irqbalance.service
  │ └ 1171 irqbalance
  ├ sendmail.service
  │ ├ 1430 sendmail: Queue runner@01:00:00 for /var/spool/clientmqueue
  │ └ 1434 sendmail: accepting connections
  ├ accounts-daemon.service
  │ └ 994 /usr/libexec/accounts-daemon
  ├ polkitd.service
  │ └ 986 /usr/libexec/polkit-1/polkitd
  ├ wpa_supplicant.service
  │ └ 981 /usr/sbin/wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant.conf -u
  ├ bluetooth.service
  │ └ 980 /usr/sbin/bluetoothd -n
  ├ udisks.service
  │ ├ 978 /usr/libexec/udisks-daemon
  │ └ 993 udisks-daemon: polling /dev/sr0
  ├ dbus.service
  │ └ 1010 /bin/dbus-daemon --system --address=systemd: --nofork --systemd-activation
  ├ auditd.service
  │ ├ 975 /sbin/auditd -n
  │ ├ 988 /sbin/audispd
  │ └ 997 /usr/sbin/sedispatch
  ├ console-kit-daemon.service
  │ └ 971 /usr/sbin/console-kit-daemon --no-daemon
  ├ rsyslog.service
  │ └ 969 /sbin/rsyslogd -n -c 4
  ├ rtkit-daemon.service
  │ └ 968 /usr/libexec/rtkit-daemon
  ├ haldaemon.service
  │ ├  967 /usr/sbin/hald --daemon=no --use-syslog
  │ ├ 1014 hald-runner
  │ ├ 1275 hald-addon-input: Listening on /dev/input/event3 /dev/input/event7 /dev/input/event6 /dev/input/event1 /dev/input/event4 /dev/input/event2 /dev/input/event0 /dev/input/event9
  │ ├ 1281 /usr/libexec/hald-addon-rfkill-killswitch
  │ ├ 1299 /usr/libexec/hald-addon-leds
  │ ├ 1301 /usr/libexec/hald-addon-generic-backlight
  │ └ 1308 /usr/libexec/hald-addon-acpi
  ├ upowerd.service
  │ └ 966 /usr/libexec/upowerd
  ├ abrtd.service
  │ └ 963 /usr/sbin/abrtd -d -s
  ├ rpcbind.service
  │ └ 961 /sbin/rpcbind -f
  ├ cups.service
  │ └ 1005 /usr/sbin/cupsd -f
  ├ modem-manager.service
  │ └ 955 /usr/sbin/modem-manager
  ├ crond.service
  │ └ 951 /usr/sbin/crond -n
  ├ atd.service
  │ └ 950 /usr/sbin/atd -f
  ├ acpid.service
  │ └ 949 /usr/sbin/acpid -f
  ├ NetworkManager.service
  │ ├  946 /usr/sbin/NetworkManager --no-daemon
  │ └ 1319 /sbin/dhclient -d -4 -sf /usr/libexec/nm-dhcp-client.action -pf /var/run/dhclient-eth0.pid -lf /var/lib/dhclient/dhclient-5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03-eth0.lease -cf /var/run/nm-dhclient-eth0.conf eth0
  ├ avahi-daemon.service
  │ ├ 944 avahi-daemon: running [lambda.local]
  │ └ 957 avahi-daemon: chroot helper
  ├ hdapsd@.service
  │ └ sda
  │   └ 940 /usr/sbin/hdapsd -d sda
  ├ dev-mqueue.mount
  ├ dev-hugepages.mount
  └ sysinit.service
    ├ 414 /sbin/udevd -d
    ├ 468 /sbin/udevd -d
    └ 469 /sbin/udevd -d

What other units does a unit depend on?

For example, if you want to figure out which services a target like multi-user.target pulls in, use something like this: 

$ systemctl show -p "Wants" multi-user.target
Wants=rc-local.service avahi-daemon.service rpcbind.service NetworkManager.service acpid.service dbus.service atd.service crond.service auditd.service ntpd.service udisks.service bluetooth.service cups.service wpa_supplicant.service getty.target modem-manager.service portreserve.service abrtd.service yum-updatesd.service upowerd.service test-first.service pcscd.service rsyslog.service haldaemon.service remote-fs.target plymouth-quit.service systemd-update-utmp-runlevel.service sendmail.service lvm2-monitor.service cpuspeed.service udev-post.service mdmonitor.service iscsid.service livesys.service livesys-late.service irqbalance.service iscsi.service netfs.service

Instead of "Wants" you might also try "WantedBy", "Requires", "RequiredBy", "Conflicts", "ConflictedBy", "Before", "After" for the respective types of dependencies and their inverse.

What would get started if I booted into a specific target?

If you want systemd to calculate the "initial" transaction it would execute on boot, try something like this: 

$ systemd --test --system --unit=foobar.target

for a boot target foobar.target. Note that this is mostly a debugging tool that actually does a lot more than just calculate the initial transaction, so don't build scripts based on this.