Go Ubuntu System UPDATE-RC.D Command

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The UPDATE-RC.D command in Ubuntu or the Debian system is the script used to update the system startup items. The links to these scripts are located in the/etc/rcn.d/directory, and the corresponding scripts are located in the/etc/init.d/directory. Before you know the UPDATE-RC.D command, you need to know about the main boot steps of the Linux system, as well as the knowledge of the operating level in Ubuntu.

First, the Linux system main boot step

1. Read the information from the MBR and start boot Manager.
2. Load the system kernel, start the init process, the init process is the root process of Linux, all system processes are its child processes.
3. The init process reads the information from the/etc/inittab file and enters the preset runlevel. Typically, the startup script under the/etc/rcs.d/directory is executed first, followed by the/etc/rcn.d/directory.
4. Start the Xwindow server Xorg,xwindow as a graphical user interface system under Linux based on the corresponding script in the/etc/rcs.d/folder.
5. Start the login manager and wait for the user to log on.

Operational level in Ubuntu

• 0 (Shut down the system)
• 1 (Single-user mode, only allows root users to maintain the system.) ）
• 2 to 5 (multi-user mode, where 3 is the character interface and 5 is the graphical interface. ）
• 6 (Restart System)

Switching the Run level

init [0123456Ss] Example: init 0 command shutdown; Init 6 command restart

　

Startup Item Management Tool

sudo install sysv-rc-conf//or using tools with GUI Bumsudo sysv-rc-conf

Iii. update-rc.d command to remove a specified startup item from all RunLevel

Update-rc.d-f 
   
     Remove
   

Start or close in specified order, in the specified run level

UPDATE-RC.D 
   
     start|stop 
     
     
       instance: Update-rc.d apachectl start 20 2 3 4 5. Stop 20 0 1 6.
     
    
   

Resolution: expressed in the 2, 3, 4, 5 of these five runlevel, from small to large, the 20th start to run Apachectl, in 0 1 6 of these 3 RunLevel, 20th closes Apachectl. This is the combination of the wording, note that it has 2 points, the effect equals the following method:

UPDATE-RC.D Apachectl Defaults

A starts after B to start, B shuts down after

UPDATE-RC.D A defaults 20update-rc.d B Defaults 90 10

Start and close order is 90, level default

UPDATE-RC.D 
   
     Defaults 90
   

　　

Go Ubuntu System UPDATE-RC.D Command