Backwards Compatibility
The transition to using systemd is made easier by the fact the service and chkconfig commands are still available. They have been reworked to call the equivalent systemctl commands. What’s more, they sometimes output the command they are redirecting too, making learning the new systemd commands much easier.
# service nfs restart
Redirecting to /bin/systemctl restart nfs.service
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On Fedora, this backwards compatibility also extends to the system-config-services tool, which is still available. This package is not available in the RHEL7/OL7 distributions.
Starting and Stopping Services
When using sysvint these actions were achieved using the service command, with the service definitions located in the “/etc/init.d” directory. Under systemd, the service definitions are located in the “/lib/systemd/system/” directory.
# ls /lib/systemd/system/httpd.service
/lib/systemd/system/httpd.service
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The systemctl command is used to stop, start, restart and check the status of a specified service. Unlike the service command, most systemctl commands do not produce any status output on the command line. Services can be referenced with or without the “.service” suffix.
# systemctl stop httpd
# systemctl stop httpd.service
# systemctl start httpd
# systemctl start httpd.service
# systemctl restart httpd
# systemctl restart httpd.service
# systemctl status httpd
# systemctl status httpd.service
The output from the systemctl status command is quite different to that of the service command.
# systemctl status httpd
httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
Active: active (running) since Sun 2014-04-20 09:26:18 BST; 32min ago
Main PID: 16314 (httpd)
Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
CGroup: /system.slice/httpd.service
├─16314 /usr/sbin/httpd -DFOREGROUND
├─16315 /usr/sbin/httpd -DFOREGROUND
├─16316 /usr/sbin/httpd -DFOREGROUND
├─16317 /usr/sbin/httpd -DFOREGROUND
├─16318 /usr/sbin/httpd -DFOREGROUND
└─16319 /usr/sbin/httpd -DFOREGROUND
Apr 20 09:26:18 localhost.localdomain systemd[1]: Starting The Apache HTTP Se...
Apr 20 09:26:18 localhost.localdomain httpd[16314]: AH00558: httpd: Could not...
Apr 20 09:26:18 localhost.localdomain systemd[1]: Started The Apache HTTP Ser...
Hint: Some lines were ellipsized, use -l to show in full.
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Use the following commands to get the status of all services.
# # All loaded and active services.
# systemctl list-units --type service
# # All loaded services
# systemctl list-units --type service --all
# # All available services
# systemctl list-unit-files --type service
Enabling and Disabling Services
Under sysvint the chkconfig command was used to perform these actions. Under systemd the systemctl command is used to enable and disable services to auto-start at reboot.
# systemctl enable httpd
ln -s '/usr/lib/systemd/system/httpd.service' '/etc/systemd/system/multi-user.target.wants/httpd.service'
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# systemctl disable httpd
rm '/etc/systemd/system/multi-user.target.wants/httpd.service'
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system-config-services
On Fedora the “Service Configuration” dialog is available from the menu (System > Administration > Services) or directly from the command line by running the system-config-services command.
The “Enable” and “Disable” buttons are used to toggle the auto-start on reboot for each service. The “Start”, “Stop” and “Restart” buttons affect the current state of the service.
Creating Linux Services
As an example, in this section we will create a new service to automatically start/stop an Oracle database. This assumes the Oracle database is not using Oracle Restart and the “start_all.sh” and “stop_all.sh” scripts are already present, as described here.
Create the service file called “/lib/systemd/system/dbora.service”.
[Unit]
Description=The Oracle Database Service
After=syslog.target network.target
[Service]
# systemd ignores PAM limits, so set any necessary limits in the service.
# Not really a bug, but a feature.
# <https://bugzilla.redhat.com/show_bug.cgi?id=754285>
LimitMEMLOCK=infinity
LimitNOFILE=65535
#Type=simple
# idle: similar to simple, the actual execution of the service binary is delayed
# until all jobs are finished, which avoids mixing the status output with shell output of services.
RemainAfterExit=yes
User=oracle
Group=oinstall
Restart=no
ExecStart=/bin/bash -c '/home/oracle/scripts/start_all.sh'
ExecStop=/bin/bash -c '/home/oracle/scripts/stop_all.sh'
[Install]
WantedBy=multi-user.target
Thanks to Javier and Mark in the comments for their suggestions about using RemainAfterExit, User and Group in this file.
If you are using NFS storage, you need to define the dependency between Oracle and NFS.
[Unit]
Description=The Oracle Database Service
Requires=rpc-statd.service network.target nfs.service nfs-mountd.service local-fs.target remote-fs.target
After=syslog.target network.target nfs.service nfs-mountd.service local-fs.target rpc-statd.service remote-fs.target
[Service]
# systemd ignores PAM limits, so set any necessary limits in the service.
# Not really a bug, but a feature.
# <https://bugzilla.redhat.com/show_bug.cgi?id=754285>
LimitMEMLOCK=infinity
LimitNOFILE=65535
#Type=simple
# idle: similar to simple, the actual execution of the service binary is delayed
# until all jobs are finished, which avoids mixing the status output with shell output of services.
Type=idle
RemainAfterExit=yes
User=oracle
Group=oinstall
Restart=no
ExecStart=/bin/bash -c '/home/oracle/scripts/start_all.sh'
ExecStop=/bin/bash -c '/home/oracle/scripts/stop_all.sh'
[Install]
WantedBy=multi-user.target
Thanks to Fr3dY in the comments for pointing out the NFS dependency management using Requires and After and the issue with systemd and PAM limits.
Reload systemd so it can see the new service.
# systemctl daemon-reload
Start the service and enable so it is automatically restarted on reboot.
# systemctl start dbora.service
# systemctl enable dbora.service
ln -s '/usr/lib/systemd/system/dbora.service' '/etc/systemd/system/multi-user.target.wants/dbora.service'
# systemctl status dbora.service
dbora.service - The Oracle Database Service
Loaded: loaded (/lib/systemd/system/dbora.service; linked)
Active: active (exited) since Tue 2015-03-24 10:55:28 GMT; 5min ago
Process: 6145 ExecStart=/home/oracle/scripts/start_all.sh (code=exited, status=0/SUCCESS)
Main PID: 6145 (code=exited, status=0/SUCCESS)
Mar 24 10:56:27 ol7-121.localdomain startup.sh[6145]: SQL> ORACLE instance started.
Mar 24 10:56:27 ol7-121.localdomain startup.sh[6145]: Total System Global Area 1140850688 bytes
Mar 24 10:56:27 ol7-121.localdomain startup.sh[6145]: Fixed Size 2923584 bytes
Mar 24 10:56:27 ol7-121.localdomain startup.sh[6145]: Variable Size 419431360 bytes
Mar 24 10:56:27 ol7-121.localdomain startup.sh[6145]: Database Buffers 704643072 bytes
Mar 24 10:56:27 ol7-121.localdomain startup.sh[6145]: Redo Buffers 13852672 bytes
Mar 24 10:56:31 ol7-121.localdomain startup.sh[6145]: Database mounted.
Mar 24 10:56:33 ol7-121.localdomain startup.sh[6145]: Database opened.
Mar 24 10:56:33 ol7-121.localdomain startup.sh[6145]: SQL> Disconnected from Oracle Database 12c Enterprise Edition Re...ction
Mar 24 10:56:33 ol7-121.localdomain startup.sh[6145]: With the Partitioning, OLAP, Advanced Analytics and Real Applica...tions
Hint: Some lines were ellipsized, use -l to show in full.
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