SYSTEMCTL Command Complete Guide

Systemctl is a systemd tool that is primarily responsible for controlling SYSTEMD systems and service managers. Systemd is a collection of systems management daemons, tools, and libraries that supersede the System V initial process. The SYSTEMD feature is for centralized management and configuration of Unix-like systems. In the Linux ecosystem, SYSTEMD is deployed in most of the standard Linux distributions, with only a few distributions yet to be deployed. SYSTEMD is usually the parent process of all other daemons, but not always. Managing Linux Services with Systemctl This article is intended to illustrate "How to control systems and services" on systems running SYSTEMD. SYSTEMD first experience and Systemctl Foundation 1. First check if the SYSTEMD is installed on your system and determine which version is currently installed # SYSTEMD--version SYSTEMD 215 +pam +audit +selinux +ima +sysvinit +libcryptsetup +gcrypt +acl +xz-seccomp-apparmor It is clear from the example above that we have installed the 215 version of SYSTEMD. 2. Check the installation location of binaries and library files for Systemd and Systemctl # 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 if the SYSTEMD is running # Ps-eaf | grep [S]ystemd Root 10016:27?00:00:00/usr/lib/systemd/systemd--switched-root--system--deserialize 23 Root 4441016:27?00:00:00/usr/lib/systemd/systemd-journald Root 4691016:27?00:00:00/USR/LIB/SYSTEMD/SYSTEMD-UDEVD Root 5551016:27?00:00:00/usr/lib/systemd/systemd-logind Dbus 5561016:27?00:00:00/bin/dbus-daemon--system--address=systemd:--nofork--nopidfile--systemd-activation Note: SYSTEMD is run as a parent process (pid=1). In the PS command output with the (-e) parameter above, select All processes, (-a) Select all processes except the leading of the session, and use the (-f) parameter to output a complete list of formats (that is,-eaf). Also note the brackets and the remainder of the example in the previous example. The square bracket expression is part of the character class expression of grep. 4. Analyzing the SYSTEMD startup process # Systemd-analyze Startup finished in487ms (kernel) +2.776s (INITRD) +20.229s (userspace) =23.493s 5. Analyze the time spent by each process at startup # 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 the critical chain at startup # Systemd-analyze Critical-chain The time after the unit is active or started are printed after the "@" character. The time the unit takes to start was 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\[email protected] Important: Systemctl accepts a service (. Service), Mount Point (. mount), socket interface (. socket), and device (. device) as a unit. 7. List all 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 Arbitraryexecutablefileformatsfilesyste 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 desktopadapter Sys-devices-pc ... 00:05.0-sound-card0.device loaded active plugged 82801AA AC ' $ 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 cell (such as Cron.service) is enabled # Systemctl is-enabled Crond.service Enabled 11. Check if a cell or service is running # SYSTEMCTL Status Firewalld.service firewalld.service-firewalld-dynamic Firewall daemon Loaded:loaded (/usr/lib/systemd/system/firewalld.service; enabled) Active:active (running) since tue2015-04-2816:27:55 ist;34min ago Main pid:549 (FIREWALLD) Cgroup:/system.slice/firewalld.service └─549/usr/bin/python-es/usr/sbin/firewalld--nofork--nopid apr2816:27:51 tecmint systemd[1]:starting firewalld-dynamic Firewall daemon ... apr2816:27:55 tecmint systemd[1]:started firewalld-dynamic Firewall daemon. Using Systemctl to control and manage services 12. List all services (both 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 .... How to start, restart, stop, reload, and check the status of services (such as 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-theapache HTTP Server Loaded:loaded (/usr/lib/systemd/system/httpd.service; enabled) Active:active (running) since tue2015-04-2817:21:30 ist;6s ago Process:2876execstop=/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 apr2817:21:30 tecmint systemd[1]:startingtheapache HTTP Server ... Apr2817:21:30 tecmint httpd[2881]: AH00558:httpd:Couldnot reliably determine the server ' s fully q...ssage APR 17:21:30 tecmint systemd[1]: Started the Apache HTTP Server. Hint:some lines were ellipsized, use-l to show on full. Note: When we use Systemctl's start,restart,stop and reload commands, we do not get any output from the terminal, only the status command can print the output. 14. How to activate the service and enable or disable the service at startup (that is, start the service automatically when the system starts) # Systemctl Is-active Httpd.service # Systemctl Enable Httpd.service # systemctl Disable Httpd.service 15. How to block (let it not start) or display services (such as 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. Kill the service using the SYSTEMCTL command # Systemctl Kill httpd # SYSTEMCTL Status httpd Httpd.service-theapache HTTP Server Loaded:loaded (/usr/lib/systemd/system/httpd.service; enabled) Active:failed (Result:exit-code) since tue2015-04-2818:01:42 ist;28min ago Main pid:2881 (code=exited, status=0/success) Status: "Total requests:0; Current requests/sec:0; Current traffic:0 b/sec " Apr2817:37:29 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. Apr2817:37:29 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. apr2817:37:39 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. apr2817:37:39 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. apr2817:37:49 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. apr2817:37:49 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. apr2817:37:59 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. apr2817:37:59 tecmint systemd[1]: Httpd.service:Got notification message from the PID 2881, but recepti...bled. Apr2818:01:42 tecmint systemd[1]: Httpd.service:control process exited, code=exited status=226 apr2818:01:42 Tecmint Systemd[1]:unit Httpd.service entered failed state. Hint:some lines were ellipsized,use-l to show on full. Using Systemctl to control and manage mount points 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. Mount, Unmount, re-mount, reload the system mount point and check the status of the mount point in the system # Systemctl Start Tmp.mount # Systemctl Stop Tmp.mount # systemctl Restart Tmp.mount # Systemctl Reload Tmp.mount # SYSTEMCTL Status Tmp.mount Tmp.mount-temporarydirectory loaded:loaded (/usr/lib/systemd/system/tmp.mount; disabled) Active:active (mounted) since tue2015-04-2817:46:06 ist;2min48s ago Where:/tmp What:tmpfs Docs:man:hier (7) Http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems Process:3908execmount=/bin/mount tmpfs/tmp-t tmpfs-o mode=1777,strictatime (code=exited, Status=0/SUCCESS) apr2817:46:06 tecmint systemd[1]:mountingtemporarydirectory ... apr2817:46:06 tecmint systemd[1]: tmp.mount:directory/tmp to mount over isnot empty, mounting anyway. apr2817:46:06 Tecmint systemd[1]:mountedtemporarydirectory. 19. Activate, enable, or disable mount points at startup (automatically mount when system starts) # Systemctl Is-active Tmp.mount # Systemctl Enable Tmp.mount # systemctl Disable Tmp.mount 20. Block (Let it not enable) or visible mount point 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 ' Using Systemctl to control and manage socket interfaces 21. List all available system socket interfaces # 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 Unit files listed. 22. Start, restart, stop, reload, and check the status of the 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 printingservicesockets Loaded:loaded (/usr/lib/systemd/system/cups.socket; enabled) Active:active (listening) since tue2015-04-2818:10:59 ist;8s ago Listen:/var/run/cups/cups.sock (Stream) apr2818:10:59 tecmint systemd[1]:starting CUPS printingservicesockets. apr2818:10:59 tecmint systemd[1]:listening on CUPS printingservicesockets. 23. Activate the socket interface at startup and enable or disable it (self-booting at system startup) # Systemctl Is-active Cups.socket # Systemctl Enable Cups.socket # systemctl Disable Cups.socket 24. Shield (make it unable to start) or display socket interface # Systemctl Mask Cups.socket Ln-s '/dev/null '/etc/systemd/system/cups.socket ' # Systemctl unmask Cups.socket RM '/etc/systemd/system/cups.socket ' CPU utilization (sub-quota) of the service 25. Get CPU credits for a current service (such as httpd) # systemctl Show-p cpushares Httpd.service cpushares=1024 Note: The default CPU allocation share for each service = 1024, you can increase/decrease the CPU allocation share of a process. 26. Limit the CPU allocation share for a service (Httpd.service) to cpushares/ # systemctl Set-property Httpd.service cpushares=2000 # systemctl Show-p cpushares Httpd.service cpushares=2000 Note: When you set cpushares for a service, a directory named after the service name is automatically created (such as Httpd.service), which contains a file called 90-cpushares.conf, which contains cpushare restricted information, you can view the file in the following ways: # vi/etc/systemd/system/httpd.service.d/90-cpushares.conf [Service] cpushares=2000 27. Check all configuration details for a service # Systemctl Show httpd Id=httpd.service Names=httpd.service Requires=basic.target Wants=system.slice Wantedby=multi-user.target Conflicts=shutdown.target Before=shutdown.target Multi-user.target After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice Description=theapache HTTP Server loadstate=loaded Activestate=active Substate=running Fragmentpath=/usr/lib/systemd/system/httpd.service .... 28. Analyze the critical chain of a service (HTTPD) # Systemd-analyze Critical-chain Httpd.service The time after the unit is active or started are printed after the "@" character. The time the unit takes to start was printed after the "+" character. Httpd.service +142ms └─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\[email protected]+149ms └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\[email protected] 29. Get a list of dependencies for a service (HTTPD) # Systemctl List-dependencies Httpd.service Httpd.service ├─system.slice └─basic.target ├─firewalld.service ├─microcode.service ├─rhel-autorelabel-mark.service ├─rhel-autorelabel.service ├─rhel-configure.service ├─rhel-dmesg.service ├─rhel-loadmodules.service ├─paths.target ├─slices.target │├─-.slice │└─system.slice ├─sockets.target │├─dbus.socket .... 30. List control groups by rank # Systemd-cgls ├─1/usr/lib/systemd/systemd--switched-root--system--deserialize 23 ├─user.slice │└─user-0.slice │└─session-1.scope │├─2498 sshd: [Email protected]/0 │├─2500-bash │├─4521 Systemd-cgls │└─4522 Systemd-cgls └─system.slice ├─httpd.service │├─4440/usr/sbin/httpd-dforeground │├─4442/usr/sbin/httpd-dforeground │├─4443/usr/sbin/httpd-dforeground │├─4444/usr/sbin/httpd-dforeground │├─4445/usr/sbin/httpd-dforeground │└─4446/usr/sbin/httpd-dforeground ├─polkit.service │└─721/USR/LIB/POLKIT-1/POLKITD--no-debug .... 31. List control groups by CPU, memory, input, and output # Systemd-cgtop PATHTASKS%CPU memoryinput/s output/s /831.0437.8m-- /system.slice-0.1--- /system.slice/mariadb.service 20.1--- /system.slice/tuned.service 10.0--- /system.slice/httpd.service 60.0--- /system.slice/networkmanager.service 1---- /system.slice/atop.service 1---- /system.slice/atopacct.service 1---- /system.slice/auditd.service 1---- /system.slice/crond.service 1---- /system.slice/dbus.service 1---- /system.slice/firewalld.service 1---- /system.slice/lvm2-lvmetad.service 1---- /system.slice/polkit.service 1---- /system.slice/postfix.service 3---- /system.slice/rsyslog.service 1---- /system.slice/system-getty.slice/[email protected] 1---- /system.slice/systemd-journald.service 1---- /system.slice/systemd-logind.service 1---- /system.slice/systemd-udevd.service 1---- /system.slice/webmin.service 1---- /USER.SLICE/USER-0.SLICE/SESSION-1.SCOPE3---- Control system operating level 32. Start the System rescue mode # Systemctl Rescue Broadcast message from [e-mail protected] on pts/0 (wed2015-04-2911:31:18 IST): The system is going down to rescue mode now! 33. Enter Emergency mode # SYSTEMCTL Emergency Welcome to emergency mode! After logging in, type ' JOURNALCTL-XB ' to view System logs, "Systemctl reboot" to reboot, "systemctl default" to try again To boot Intodefault mode. 34. List the currently used run level # Systemctl Get-default Multi-user.target 35. Start the operation level 5, that is, the graphics mode # Systemctl Isolate Runlevel5.target Or # Systemctl Isolate Graphical.target 36. Start Run Level 3, which is multi-user mode (command line) # Systemctl Isolate Runlevel3.target Or # Systemctl Isolate Multiuser.target 36. Set the default run level for multi-user mode or graphics mode # Systemctl Set-default Runlevel3.target # Systemctl Set-default Runlevel5.target 37. Restart, stop, suspend, hibernate the system or bring the system into mixed sleep # Systemctl reboot # Systemctl Halt # Systemctl Suspend # Systemctl Hibernate # Systemctl Hybrid-sleep For those who do not know what the operating level is, explain the following. Runlevel 0: Shutting down the system Runlevel 1: Rescue? Maintenance Mode Runlevel 3: Multi-user, no graphics system Runlevel 4: Multi-user, no graphics system Runlevel 5: Multi-user, graphical system Runlevel 6: Close and restart the machine That's it. Stay connected and make comments. Don't forget to give us some valuable feedback in the comments below. Like us, share with us, seek to spread.

SYSTEMCTL Command Complete Guide