![]() This module allows you to create and edit the scripts that are run at bootup and shutdown time, called actions by the module. Of course, if you are using Webmin you don't have to worry about the locations of any of these directories as it always knows where they are. Fortunately, /etc/rc.d seems to be becoming the standard base directory in newer distributions. Some use /etc/init.d for the actual script files, while others (such as older versions of SuSE) put everything in the /sbin directory. Not all Linux distributions use these directories for their bootup scripts. So /etc/rc.d/rc5.d/S10network would be run in runlevel 5 before /etc/rc.d/rc5.d/S80sendmail. Each symbolic link has a name like S_YY_scriptname, in which YY is the order that the script is started in the boot process - the lower the number, the earlier the script starts. The scripts that are started or stopped in each runlevel are determined by symbolic links from the /etc/rc.d/rc_X_.d directory, where X is the runlevel number. The directory /etc/rc.d/init.d is usually used to store the actual bootup shell scripts. See the section below on the SysV Init Configuration module for information on how to change the bootup runlevel. This runlevel is useful if some bootup script is failing and making your system un-bootable. ![]() 1 - Single user mode Only the most basic system initialization is done, and a root shell opened on the console. 2 - Multi-user mode without NFS Almost all servers and services are started, but NFS filesystems are not mounted. 3 - Multi-user mode All servers and services are started, but only the normal text login is available on the console. The commonly used runlevels are:ĥ - Graphical mode All servers and services will be started, and X started to display a graphical login prompt on the console. The runlevel can be set by the boot loader, or by the /etc/inittab file. When a Linux system starts up, different scripts are executed depending on which runlevel it is starting in. If requested and supported by the hardware, the last step in the shutdown process will be the powering off of the system by the kernel. These scripts also have a fixed order, so that the de-activation of networking and other basic services happens last. The scripts have a fixed order that they must execute in, as some of the later scripts are dependant on earlier ones - for example, network filesystems cannot be mounted until network interfaces have been enabled.Īt shutdown time, a series of scripts is also run to shut down servers and un-mount filesystems. ![]() Each of these scripts is responsible for a single task, such as initializing network interfaces, starting a webserver or mounting other filesystems. ![]() It reads the /etc/inittab file and executes the commands it specifies, the most important of which begins execution of bootup scripts. Once the kernel has been loaded, it mounts the root filesystem runs the init program, which is responsible for managing the rest of the boot process. There are several boot loaders available for Linux such as LILO and GRUB, but they all do basically the same thing. This piece of code is called a boot loader, and is responsible for displaying a menu of operating systems to the user and loading one of them. The BIOS (Basic Input/Output System) performs memory and other hardware checks, then loads a tiny piece of code from the first part of one of the system's hard disks, known as the master boot record or MBR. The very first thing to happen when a PC starts up is the loading of the BIOS from ROM.
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