Master Linux Autostart: Manage Runlevels, Add & Remove Services Easily

Autostart services are crucial for Linux systems, whether you need to add a service manually, remove an unwanted one, or eliminate malicious entries.

The runlevel mechanism is implemented through the directories /etc/rc.d/rc0.d … /etc/rc.d/rc6.d, each representing one of the seven Linux runlevels defined in /etc/inittab. When the system enters a runlevel, it processes the scripts in the corresponding rcN.d directory in lexical order.

Each entry in rcN.d is a symbolic link to a script in /etc/init.d. The naming convention uses a leading K (kill) or S (start) followed by a two‑digit order number and the service name, e.g., K20network or S99apache.

The seven runlevels are:

0 – Halt

1 – Single‑user mode (root only, no remote login)

2 – Multi‑user without NFS

3 – Standard multi‑user, command‑line

4 – Reserved

5 – Multi‑user with graphical interface

6 – Reboot

Servers typically run at level 3.

Adding an autostart program

1. Create a script in /etc/init.d. Example for SVN:

#!/bin/bash
svnserve -d -r /svn仓库路径

2. Make it executable: chmod 755 /etc/init.d/svn 3. Link it into the desired runlevel directory, e.g., level 3: ln -s /etc/init.d/svn /etc/rc.d/rc3.d/S101svn The S prefix indicates the script should be started, and the number (101) defines the execution order; values greater than 60 ensure basic services start first.

2. Alternatively, add commands to /etc/rc.local, which runs after all runlevel scripts.

3. The chkconfig command can also manage services.

Disabling an autostart program

Delete the corresponding link in /etc/rc.d/rcN.d.

Remove entries from /etc/rc.local.

Use chkconfig --list to view services and chkconfig --del <service_name> to disable them.