Linux system boot level

Linux Run Level

To enter Linux as an administrator, modify the file:/etc/inittab

Find "Id:5:initdefault:" 5 of which is X-window, which is the default RunLevel

Linux starts running at one level, and these run levels are listed below:

0 System Stop

1 Single user system, no login required

2 Multi-user system but NFS not supported, command-line mode login

3 full multi-user mode, command-line mode login

4 Not used

5 X11 Graphics mode, graphical mode login

6 Rebooting the system

These can be seen in the /etc/initab file in 0-6 levels of comments, the code snippet is as follows:

# Default RunLevel. The runlevels used are:#   this) #   1-Single user mode#   ifdo not having networking) #   3-Full multiuser mode#   4- unused#   5- X 11#   This) # ID:5:initdefault:

1. Level 0

The system stops. Be careful not to set this level to the default mode, or the system will stop automatically after each boot and cannot be entered.

This runlevel is primarily used to close tasks, and the individual connection commands in the RC0.D directory are commands at this level. When closed, these commands are executed one by one. They will kill all processes, shut down virtual memory and swap files, unmount the file system, and swap partitions.

The shutdown operation is completely different under DOS and Linux. At the DOS prompt, you can safely turn off the power directly. However, it is not possible to do so under Linux. The Linux file system is mounted at startup and is uninstalled when it is closed. This difference is the premise of Linux's powerful capabilities.

Under Linux, to shut down, restart the computer, or by pressing the hotkey "Ctrl" + "Alt" + "Del" to restart by entering the command shutdown plus parameters.

2. Level 1

Single-user mode. This mode only permits one user to log on to all files in the RC1.D directory from the local computer to be connected to this runlevel. This runlevel is typically used for system management and maintenance, such as upgrading Linux systems, installing new software, and so on.

In this mode, only the administrator can enter and other users cannot log on. Because the file system is loaded at startup and the network is not loaded, you cannot log on through the network.

3. Level 2

Multi-user mode. Users can log on through the network. In cases where the network is not supported, the mode and mode 3 are phase, and all files in the RC2.D directory are connected to this level.

4. Level 3

Full multi-user mode. This is the default run mode, in which all network service programs run together. The files recorded by RC3.D are connected to this level.

5. Level 4

The RC4.D directory is connected to this level without using the pattern. This level is a user-defined runlevel that the user can define by their roots. If you want to run this level, you must put the connection file in the RC3.D directory, just like any other rc*.d directory, and indicate whether the process is started or terminated.

6. Level 5

Running X Window under Linux is the use of this level. Under this level, the named of the domain name server in addition to the Internet is different from level 3, the rest is the same.

7. Level 6

This is the runlevel for restarting the system. The RC6.D directory is connected to this level. Since it is a reboot that shuts down the current system, but does not turn off the power, the connection under this directory is basically the same as the connection at level 0 under RC0.D. The difference is that although they all execute the halt (Close) command, the parameters passed to the halt are different, so level 6 can reboot the system.

Linux system boot level