How to Manage ‘Systemd’ Services and Units Using ‘Systemctl’ in Linux

Systemctl is a systemd utility which is responsible for Controlling the systemd system and service manager.

Systemd is a collection of system management daemons, utilities and libraries which serves as a replacement of System V init daemon. Systemd functions as central management and configuration platform for UNIX like system.

In the Linux Ecosystem Systemd has been implemented on most of the standard Linux Distribution with a few exception. Systemd is the parent Process of all other daemons oftenly but not always.

Manage Linux Services Using Systemctl

Manage Linux Services Using Systemctl

This article aims at throwing light on “How to control System and Services” on a system running systemd.

Starting with Systemtd and Systemctl Basics

1. First check if systemd is installed on your system or not and what is the version of currently installed Systemd?

# systemd --version

systemd 215
+PAM +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ -SECCOMP -APPARMOR

It’s clear from the above example, that we have systemd 215 version Installed.

2. Check where the binaries and libraries of systemd and systemctl are installed.

# whereis systemd 
systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz


# whereis systemctl
systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz

3. Check whether systemd is running or not.

# ps -eaf | grep [s]ystemd

root         1     0  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
root       444     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-journald
root       469     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-udevd
root       555     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-logind
dbus       556     1  0 16:27 ?        00:00:00 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation

Notice: systemd is running as parent daemon (PID=1). In the above command ps with (-e) select all Processes, (-a) select all processes except session leaders and (-f) for full format listing (i.e. -eaf).

Also note the square brackets in the above example and rest of the examples to follow. Square Bracket expression is part of grep’s character class pattern matching.

4. Analyze systemd boot process.

# systemd-analyze
Startup finished in 487ms (kernel) + 2.776s (initrd) + 20.229s (userspace) = 23.493s

5. Analyze time taken by each process at boot.

# systemd-analyze blame

8.565s mariadb.service
7.991s webmin.service
6.095s postfix.service
4.311s httpd.service
3.926s firewalld.service
3.780s kdump.service
3.238s tuned.service
1.712s network.service
1.394s lvm2-monitor.service
1.126s systemd-logind.service
....

6. Analyze critical chain at boot.

# systemd-analyze critical-chain

The time after the unit is active or started is printed after the "@" character.
The time the unit takes to start is printed after the "+" character.

multi-user.target @20.222s
└─mariadb.service @11.657s +8.565s
  └─network.target @11.168s
    └─network.service @9.456s +1.712s
      └─NetworkManager.service @8.858s +596ms
        └─firewalld.service @4.931s +3.926s
          └─basic.target @4.916s
            └─sockets.target @4.916s
              └─dbus.socket @4.916s
                └─sysinit.target @4.905s
                  └─systemd-update-utmp.service @4.864s +39ms
                    └─auditd.service @4.563s +301ms
                      └─systemd-tmpfiles-setup.service @4.485s +69ms
                        └─rhel-import-state.service @4.342s +142ms
                          └─local-fs.target @4.324s
                            └─boot.mount @4.286s +31ms
                              └─[email protected]\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096
                                └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4

Important: Systemctl accepts services (.service), mount point (.mount), sockets (.socket) and devices (.device) as units.

7. List all the available units.

# systemctl list-unit-files

UNIT FILE                                   STATE   
proc-sys-fs-binfmt_misc.automount           static  
dev-hugepages.mount                         static  
dev-mqueue.mount                            static  
proc-sys-fs-binfmt_misc.mount               static  
sys-fs-fuse-connections.mount               static  
sys-kernel-config.mount                     static  
sys-kernel-debug.mount                      static  
tmp.mount                                   disabled
brandbot.path                               disabled
.....

8. List all running units.

# systemctl list-units

UNIT                                        LOAD   ACTIVE SUB       DESCRIPTION
proc-sys-fs-binfmt_misc.automount           loaded active waiting   Arbitrary Executable File Formats File Syste
sys-devices-pc...0-1:0:0:0-block-sr0.device loaded active plugged   VBOX_CD-ROM
sys-devices-pc...:00:03.0-net-enp0s3.device loaded active plugged   PRO/1000 MT Desktop Adapter
sys-devices-pc...00:05.0-sound-card0.device loaded active plugged   82801AA AC'97 Audio Controller
sys-devices-pc...:0:0-block-sda-sda1.device loaded active plugged   VBOX_HARDDISK
sys-devices-pc...:0:0-block-sda-sda2.device loaded active plugged   LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
sys-devices-pc...0-2:0:0:0-block-sda.device loaded active plugged   VBOX_HARDDISK
sys-devices-pl...erial8250-tty-ttyS0.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS0
sys-devices-pl...erial8250-tty-ttyS1.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS1
sys-devices-pl...erial8250-tty-ttyS2.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS2
sys-devices-pl...erial8250-tty-ttyS3.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS3
sys-devices-virtual-block-dm\x2d0.device    loaded active plugged   /sys/devices/virtual/block/dm-0
sys-devices-virtual-block-dm\x2d1.device    loaded active plugged   /sys/devices/virtual/block/dm-1
sys-module-configfs.device                  loaded active plugged   /sys/module/configfs
...

9. List all failed units.

# systemctl --failed

UNIT          LOAD   ACTIVE SUB    DESCRIPTION
kdump.service loaded failed failed Crash recovery kernel arming

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

1 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.

10. Check if a Unit (cron.service) is enabled or not?.

# systemctl is-enabled crond.service

enabled

11. Check whether a Unit or Service is running or not?.

# systemctl status firewalld.service

firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
   Active: active (running) since Tue 2015-04-28 16:27:55 IST; 34min ago
 Main PID: 549 (firewalld)
   CGroup: /system.slice/firewalld.service
           └─549 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Apr 28 16:27:51 tecmint systemd[1]: Starting firewalld - dynamic firewall daemon...
Apr 28 16:27:55 tecmint systemd[1]: Started firewalld - dynamic firewall daemon.

Control and Manage Services Using Systemctl

12. List all services (including enabled and disabled).

# systemctl list-unit-files --type=service

UNIT FILE                                   STATE   
arp-ethers.service                          disabled
auditd.service                              enabled 
[email protected]                             disabled
blk-availability.service                    disabled
brandbot.service                            static  
collectd.service                            disabled
console-getty.service                       disabled
console-shell.service                       disabled
cpupower.service                            disabled
crond.service                               enabled 
dbus-org.fedoraproject.FirewallD1.service   enabled 
....

13. How do I start, restart, stop, reload and check the status of a service (httpd.service) in Linux.

# systemctl start httpd.service
# systemctl restart httpd.service
# systemctl stop httpd.service
# systemctl reload httpd.service
# systemctl status httpd.service

httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
   Active: active (running) since Tue 2015-04-28 17:21:30 IST; 6s ago
  Process: 2876 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)
 Main PID: 2881 (httpd)
   Status: "Processing requests..."
   CGroup: /system.slice/httpd.service
           ├─2881 /usr/sbin/httpd -DFOREGROUND
           ├─2884 /usr/sbin/httpd -DFOREGROUND
           ├─2885 /usr/sbin/httpd -DFOREGROUND
           ├─2886 /usr/sbin/httpd -DFOREGROUND
           ├─2887 /usr/sbin/httpd -DFOREGROUND
           └─2888 /usr/sbin/httpd -DFOREGROUND

Apr 28 17:21:30 tecmint systemd[1]: Starting The Apache HTTP Server...
Apr 28 17:21:30 tecmint httpd[2881]: AH00558: httpd: Could not reliably determine the server's fully q...ssage
Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
Hint: Some lines were ellipsized, use -l to show in full.

Note: When we use commands like start, restart, stop and reload with systemctl, we will not get any output on the terminal, only status command will print the output.

14. How to active a service and enable or disable a service at boot time (auto start service at system boot).

# systemctl is-active httpd.service
# systemctl enable httpd.service
# systemctl disable httpd.service

15. How to mask (making it impossible to start) or unmask a service (httpd.service).

# systemctl mask httpd.service
ln -s '/dev/null' '/etc/systemd/system/httpd.service'

# systemctl unmask httpd.service
rm '/etc/systemd/system/httpd.service'

16. How to a Kill a service using systemctl command.

# systemctl kill httpd
# systemctl status httpd

httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
   Active: failed (Result: exit-code) since Tue 2015-04-28 18:01:42 IST; 28min ago
 Main PID: 2881 (code=exited, status=0/SUCCESS)
   Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0 B/sec"

Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 18:01:42 tecmint systemd[1]: httpd.service: control process exited, code=exited status=226
Apr 28 18:01:42 tecmint systemd[1]: Unit httpd.service entered failed state.
Hint: Some lines were ellipsized, use -l to show in full.

Control and Manage Mount Points using Systemctl

17. List all system mount points.

# systemctl list-unit-files --type=mount

UNIT FILE                     STATE   
dev-hugepages.mount           static  
dev-mqueue.mount              static  
proc-sys-fs-binfmt_misc.mount static  
sys-fs-fuse-connections.mount static  
sys-kernel-config.mount       static  
sys-kernel-debug.mount        static  
tmp.mount                     disabled

18. How do I mount, unmount, remount, reload system mount points and also check the status of mount points on the system.

# systemctl start tmp.mount
# systemctl stop tmp.mount
# systemctl restart tmp.mount
# systemctl reload tmp.mount
# systemctl status tmp.mount

tmp.mount - Temporary Directory
   Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled)
   Active: active (mounted) since Tue 2015-04-28 17:46:06 IST; 2min 48s ago
    Where: /tmp
     What: tmpfs
     Docs: man:hier(7)
           http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
  Process: 3908 ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)

Apr 28 17:46:06 tecmint systemd[1]: Mounting Temporary Directory...
Apr 28 17:46:06 tecmint systemd[1]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
Apr 28 17:46:06 tecmint systemd[1]: Mounted Temporary Directory.

19. How to active, enable or disable a mount point at boot time (auto mount at system boot).

# systemctl is-active tmp.mount
# systemctl enable tmp.mount
# systemctl disable  tmp.mount

20. How to mask (making it impossible to start) or unmask a mount points in Linux.

# systemctl mask tmp.mount

ln -s '/dev/null' '/etc/systemd/system/tmp.mount'

# systemctl unmask tmp.mount

rm '/etc/systemd/system/tmp.mount'

Control and Manage Sockets using Systemctl

21. List all available system sockets.

# systemctl list-unit-files --type=socket

UNIT FILE                    STATE   
dbus.socket                  static  
dm-event.socket              enabled 
lvm2-lvmetad.socket          enabled 
rsyncd.socket                disabled
sshd.socket                  disabled
syslog.socket                static  
systemd-initctl.socket       static  
systemd-journald.socket      static  
systemd-shutdownd.socket     static  
systemd-udevd-control.socket static  
systemd-udevd-kernel.socket  static  

11 unit files listed.

22. How do I start, restart, stop, reload and check the status of a socket (example: cups.socket) in Linux.

# systemctl start cups.socket
# systemctl restart cups.socket
# systemctl stop cups.socket
# systemctl reload cups.socket
# systemctl status cups.socket

cups.socket - CUPS Printing Service Sockets
   Loaded: loaded (/usr/lib/systemd/system/cups.socket; enabled)
   Active: active (listening) since Tue 2015-04-28 18:10:59 IST; 8s ago
   Listen: /var/run/cups/cups.sock (Stream)

Apr 28 18:10:59 tecmint systemd[1]: Starting CUPS Printing Service Sockets.
Apr 28 18:10:59 tecmint systemd[1]: Listening on CUPS Printing Service Sockets.

23. How to active a socket and enable or disable at boot time (auto start socket at system boot).

# systemctl is-active cups.socket
# systemctl enable cups.socket
# systemctl disable cups.socket

24. How to mask (making it impossible to start) or unmask a socket (cups.socket).

# systemctl mask cups.socket
ln -s '/dev/null' '/etc/systemd/system/cups.socket'

# systemctl unmask cups.socket
rm '/etc/systemd/system/cups.socket'
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18 Responses

  1. ROMSAT says:

    Superb pots. I would just like to add that all those system services also generate logs. With systemd, these logs can be managed centrally with another component called journalctl. The main configuration file is in /etc/systemd/journald.conf.
    Fear that you could dedicate another magnificent pots. Thanks a lot.

  2. Frank says:

    I would like to know about the relationship of numbering of files such as this in your teachings:
    90-CPUShares.conf

    I used a similar scheme with a .network file as seen in some tutorials. For Example:
    10-dhcp.network
    20-static.network
    30-static.network
    My belief is that the lower number .network file starts first?? Are these just arbitrary numbers? Could I use 70-dhcp.network&80.dhcp.network in the same fashion?? 99-* seems to be the last number called up.

    Also these numbers schemes look like what I see in UDEV as well…

    Keep up the great work

  3. Frank says:

    Really useful guide.
    Keep up the great work.
    I see one command not covered that I use alot.
    systemctl reenable
    This allows the unit file to reload and writes a new symbolic link to /usr/lib/

    I have also found the systemctl edit –full allows you to edit the unit control file in /etc/systemd/system folder. Helpful for setting the After= setting for controlling the startup order of services.

    • Ravi Saive says:

      @Frank,

      Thanks for appreciating our work and giving us valuable tip, we’ve will check and add to the list as per your suggestions.

      • Frank says:

        Thank You
        Just to be clear the “systemctl edit –full” needs a service to work on. For example:
        systemctl edit –full hostapd

        To this file I add-
        After=dnsmasq.service
        To have hostapd wait for dnsmasq to start first.

        It saves the file with an odd file extension that is actually the unit file. Just edit and save(ignore name). Another advantage with this method is that it reloads and reenables the service thus writing the needed symbolic links for you with a single swoop.

  4. Jan Vlčinský says:

    Nice and extensive overview of available commands.

    Question: For controlling our applications we use supervisord, which allows one-shot commands as you present here, but also provides interactive shell, where one can call commands like “start svcA”, “restart svcB”, “tail svcA”, or even “follow mode” “tail -f svcA”. The interactive mode is very handy as it does not require typing so long commands.

    Question: is there any interactive console controlling systemd defined services?

    • Ravi Saive says:

      @Jan,

      Thanks for the tips, never ever heard about supervisord, let me check how it works and also to be fact I really don’t have any idea in controlling systemd via interactive shell, let me check and get back to you..

  5. Rizal Rahman says:

    very complete handy cheat sheet that i should bookmark it now! thanks!

  6. Jalal Hajigholamali says:

    Hi,
    Very nice article
    thanks a lot

  7. sys0dm1n says:

    Thanks, I am still running nix distro with init but will be useful some day when using systemd.

    • Avishek Kumar says:

      :) if you don’t start using systemd, you will be left behind in the fast moving Linux World.

  8. CertDepot says:

    ‘systemd –version’ doesn’t work. It is ‘systemctl –version’ that works.

    • Avishek Kumar says:

      try
      # systemd-run –version

      You may thank me later. :)

      • MCBuhl says:

        I’d thank you even more if yo’d correct it in the blog post – as I had the same error as CertDepot
        + copy-pasting runs into error, too, because “–” is altered into a long “-“: Failed to find executable –version: No such file or directory

        • Donald Harvey says:

          I love the conciseness of how-to posts like this one. But yeah, fast-forward 3 yrs and ‘systemd –version’ is still in the blog post. If one needs to read comments to get the correct info, then that whole conciseness thing goes out the window.

  9. Bill M says:

    Thanks for the in-depth how-to on using the systemd control system tool. Lots of great examples!

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