Posted by CPU Utilization (Shares) of a Service
25. Get the current CPU Shares of a Service (say httpd).
# systemctl show -p CPUShares httpd.service CPUShares=1024
Note: The default each service has a CPUShare = 1024. You may increase/decrease the CPU share of a process.
26. Limit the CPU Share of a service (httpd.service) to 2000 CPUShares/
# systemctl set-property httpd.service CPUShares=2000 # systemctl show -p CPUShares httpd.service CPUShares=2000
Note: When you set CPUShare for a service, a directory with the name of service is created (httpd.service.d) which contains a file 90-CPUShares.conf which contains the CPUShare Limit information. You may view the file as:
# vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf [Service] CPUShares=2000
27. Check all the configuration details of 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=The Apache HTTP Server LoadState=loaded ActiveState=active SubState=running FragmentPath=/usr/lib/systemd/system/httpd.service ....
28. Analyze critical chain for a service (httpd).
# systemd-analyze critical-chain httpd.service
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.
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
└─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service @4.092s +149ms
└─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4.092s
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 hierarchically.
# systemd-cgls ├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 23 ├─user.slice │ └─user-0.slice │ └─session-1.scope │ ├─2498 sshd: root@pts/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 group according to CPU, memory, Input, and Output.
# systemd-cgtop Path Tasks %CPU Memory Input/s Output/s / 83 1.0 437.8M - - /system.slice - 0.1 - - - /system.slice/mariadb.service 2 0.1 - - - /system.slice/tuned.service 1 0.0 - - - /system.slice/httpd.service 6 0.0 - - - /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/getty@tty1.service 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.scope 3 - - - -
Control System Runlevels
32. How to start a system rescue mode.
# systemctl rescue Broadcast message from root@linuxtechexpert on pts/0 (Wed 2015-04-29 11:31:18 IST): The system is going down to rescue mode NOW!
33. How to enter into 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 into default mode.
34. List current run levels in use.
# systemctl get-default multi-user.target
35. How to start Runlevel 5 aka graphical mode.
# systemctl isolate runlevel5.target OR # systemctl isolate graphical.target
36. How to start Runlevel 3 aka multiuser mode (command line).
# systemctl isolate runlevel3.target OR # systemctl isolate multiuser.target
36. How to set multiuser mode or graphical mode as default run level.
# systemctl set-default runlevel3.target # systemctl set-default runlevel5.target
37. How to reboot, halt, suspend, hibernate, or put a system in hybrid-sleep.
# systemctl reboot # systemctl halt # systemctl suspend # systemctl hibernate # systemctl hybrid-sleep
For those who may not be aware of run levels and what it does.
- Runlevel 0 : Shut down and Power off the system.
- Runlevel 1 : Rescue?Maintainance Mode.
- Runlevel 3 : multiuser, no-graphic system.
- Runlevel 4 : multiuser, no-graphic system.
- Runlevel 5 : multiuser, graphical system.
- Runlevel 6 : Shutdown and Reboot the machine.
That’s all for now. Keep connected! Keep commenting. Don’t forget to provide us with your valuable feedback in the comments below. Like and share us and help us get spread.Pages: 1 2
