Systemd
Contents
Making Changes to Systemd unit files/configuration
When you have made changes to the unit file of a service on the filesystem. In order for the service to use that new configuration, we need to tell the service to reload its configuration file. So run systemctl reload <service>, to tell the service to dump the current configuration you are using and RELOAD its configuration from the filesystem into memory, and now it would use that newly modified version. Since the service was never actually terminated or stopped, it retains the same main PID.
When you do systemctl restart <service>, you terminate the service and stop it, it would dump its configuration which is in memory. Then the restart action would result in the service start up again. It will load its configuration file from the file system, load up into and now it would use the version of the configuration file that is in memory. And because the service was terminated, and restarted, the service main PID will change.
My recipe for service obliteration (be careful with the rm statements!)
$ systemctl stop [servicename] $ systemctl disable [servicename] $ rm /etc/systemd/system/[servicename] $ rm /etc/systemd/system/[servicename] # and symlinks that might be related $ rm /usr/lib/systemd/system/[servicename] $ rm /usr/lib/systemd/system/[servicename] # and symlinks that might be related $ systemctl daemon-reload $ systemctl reset-failed
- Services under /etc/systemd/system/ or /etc/systemd/system/multi-user.target.wants/ are enabled
https://superuser.com/questions/513159/how-to-remove-systemd-services
Per my customer's issue, we fixed it by:
Removing the auditd.service from /usr/lib/systemd/system so you wont be able to start the service upon bootup.
To be able to start the service again you have to run: "systemctl daemon-reload” in addition to having the <>.service file in that directory
$ sudo systemctl start firewalld.service Failed to start firewalld.service: Unit not found. $ sudo systemctl daemon-reload $ sudo systemctl start firewalld.service
Disabling a Service
To disable it, you call systemctl disable <service>. Without arguments, systemctl displays the current state, which is obviously not possible in a chroot.
Alternatively, you can also go to /etc/systemd/system/ and remove the symlink to your service (probably in the multi-user.target.wants folder).
If it is a service that is enabled by default, you need to create a symlink (named <service>.service) to /dev/null to disable it. Where the symlink needs to be depends on where in /lib/systemd/system the service is enabled.
How to list all running services
systemctl list-units --type=service --state=running UNIT LOAD ACTIVE SUB DESCRIPTION auditd.service loaded active running Security Auditing Service chronyd.service loaded active running NTP client/server crond.service loaded active running Command Scheduler dbus.service loaded active running D-Bus System Message Bus getty@tty1.service loaded active running Getty on tty1 NetworkManager.service loaded active running Network Manager polkit.service loaded active running Authorization Manager rhsmcertd.service loaded active running Enable periodic update of entitlement certificates. rsyslog.service loaded active running System Logging Service serial-getty@ttyS0.service loaded active running Serial Getty on ttyS0 sshd.service loaded active running OpenSSH server daemon sssd.service loaded active running System Security Services Daemon systemd-journald.service loaded active running Journal Service systemd-logind.service loaded active running Login Service systemd-udevd.service loaded active running udev Kernel Device Manager tuned.service loaded active running Dynamic System Tuning Daemon user@1000.service loaded active running User Manager for UID 1000 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. 17 loaded units listed. Pass --all to see loaded but inactive units, too. To show all installed unit files use 'systemctl list-unit-files'.
A Unit is an aspect of the system that systemd manages. There are various types of units. We have service units that are used for daemons. We have socket units for TCP ports. We have path units to manage files and directories. Target units as well which are groups of other units.
Every unit is represented by a unit file that has its configuration.
systemctl list-units --type=socket UNIT LOAD ACTIVE SUB DESCRIPTION dbus.socket loaded active running D-Bus System Message Bus Socket sssd-kcm.socket loaded active listening SSSD Kerberos Cache Manager responder socket systemd-coredump.socket loaded active listening Process Core Dump Socket systemd-initctl.socket loaded active listening initctl Compatibility Named Pipe systemd-journald-dev-log.socket loaded active running Journal Socket (/dev/log) systemd-journald.socket loaded active running Journal Socket systemd-udevd-control.socket loaded active running udev Control Socket systemd-udevd-kernel.socket loaded active running udev Kernel Socket 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. 8 loaded units listed. Pass --all to see loaded but inactive units, too. To show all installed unit files use 'systemctl list-unit-files'.