CentOS 7 startup services and script

1. Adding a boot service

1. Create a configuration file with the suffix service, such as creating the file test.service. The contents of the file are as follows:

   [Unit]
   Description=Test
   After=network.target
   [Service]
   Type=simple
   User=nobody
   Restart=on-failure
   RestartSec=5s
   TimeoutStartSec=0
   ExecStart=/usr/local/test
   [Install]
   WantedBy=multi-user.target

   Parameter definition:

   • After-dependency, indicating that the service is started after the network is started.
     
     How to handle dependencies:
     When using systemd, the dependencies can be resolved by writing the cell configuration file correctly. Typically, unit A requires unit B to run before A starts. In this case, add Requires=B and After=B to the [Unit] section of the unit A configuration file. If this dependency is optional, add Wants=B and After=B. Note that Wants= and Requires= do not mean After= , ie if the After= option is not specified, the two units will be started in parallel.
     
     Dependencies are often used on services rather than targets. For example, network.target is typically introduced by a service that configures a network interface, so it is sufficient to queue a custom unit after the service because network.target has already started.
   • Type-type
     
     Type=simple : (default) systemd thinks the service will start immediately. The service process will not fork. If the service is to start other services, do not use this type to start unless the service is socket activated.
     Type=forking : systemd thinks that when the service process forks and the parent process exits, the service starts successfully. For a regular daemon, you can start with this type unless you are sure that this startup method does not meet your needs. Use this startup type to specify PIDFile= at the same time so that systemd can track the main process of the service.
     Type=oneshot : This option is for a service that performs only one task and then exits immediately. It may be necessary to set RemainAfterExit=yes at the same time so that systemd still considers the service to be active after the service process exits.
     Type=notify : Same as Type=simple, but the contracted service will send a signal to systemd when it is ready. The implementation of this notification is provided by libsystemd-daemon.so.
     Type=dbus : If started in this way, when the specified BusName appears on the DBus system bus, systemd considers the service ready.
     Type=idle : systemd will wait for all tasks to be processed before starting to execute units of type idle. Other behaviors are similar to Type=simple.
   • ExecStart – The command line to start the service, including the execution file path and program parameters.
   • WantedBy-Which user group to install this service
     
     multi-user.target end user
     
     Graphical.target desktop user
     
     Default.target default user

2. Put the configuration file you just created in
   /usr/lib/systemd/system user package installation directory
   or
   /etc/systemd/system/ System Administrator Installation Directory

3. Run the following command to install the service:

   systemctl enable test.service       #installation service
   systemctl start test.service        #Startup service
   systemctl daemon-reload             #reload

2. Add a boot script

1. Move the script to the /etc/rc.d/init.d directory

   mv test.sh /etc/rc.d/init.d

2. Increase the executable permissions of the script

   chmod +x /etc/rc.d/init.d/test.sh

3. Add a script to the boot autostart project

   cd /etc/rc.d/init.d
   chkconfig --add test.sh
   chkconfig test.sh

Note:
You directly put your usual scripts written by chkconfig --add so sure to report service test.sh does not support chkconfig error, but you only need to add the following code in the head of the file test.sh where just on the next line of ! /bin/bash

#chkconfig: 345 88 14       #345 Representing permissions

2. Add a boot script（II）

The above method may cause behavior problems that are inconsistent with expectations in many cases, so I still recommends implementing the startup script in the manner recommended by Centos official:

1. Create your_startup.service file

   # touch /usr/lib/systemd/system/your_startup.service

2. Edit your_startup.service file

   # vim /usr/lib/systemd/system/your_startup.service

3. Add the following content, save and exit

   [Unit]
   Description=start your_startup service
   Requires=graphical.target
   After=graphical.target
   [Service]
   Type=forking
   User=root
   Group=root
   Restart=always
   TimeoutSec=5
   IgnoreSIGPIPE=no
   KillMode=process
   GuessMainPID=no
   RemainAfterExit=no
   ExecStart=/etc/rc.d/init.d/your_startup.sh
   [Install]
   WantedBy=graphical.target

4. Add execute permission to your_startup.sh startup script

   # chmod 755 /etc/rc.d/init.d/your_startup.sh

5. Setting startup

   # systemctl enable /usr/lib/systemd/system/your_startup.service

6. Reboot

   # reboot

7. Check if your_startup.sh started successfully?