What is the difference between linux single user mode and multi-user mode?

The difference between single-user mode and multi-user mode in Linux is: single-user mode skips the pam verification module and directly uses the system maintenance function; while multi-user mode does not skip the pam verification module, and multi-user mode This is the normal mode of server operation.

#The operating environment of this article: linux7.3 system, Dell G3 computer.

What is the difference between Linux single-user mode and multi-user mode?

Single-user mode skips the pam verification module and directly uses the system maintenance function.

Multi-user mode is generally The server is running in normal mode.

Single user mode (English: Single user mode) is a mode with superuser privileges when working on a Linux system. This mode can usually be entered by giving 1 or S parameter in the startup menu. This mode can only be entered through the boot menu when facing the host entity, thus ensuring that the super privilege is granted to the super user who has access to the host. This operation is usually used to maintain hard disk partitions or change the superuser password and other maintenance that need to be performed before the disk is mounted.

1. Single-user method

Since there are many ways to boot a Linux system, common floppy disk boot, LILO boot, GRUB boot, I will explain these methods respectively:

1.1 Floppy disk boot

When "BOOT:" appears after the floppy disk starts, you can set the startup parameters. After typing "Linux single" here, you can start the system in single-user mode.

1.2 LILO mode

When starting in LILO mode, after the LILO prompt appears, you should quickly enter kernel/boot/vmlinuz-2.4.7-10 single roo= /dev/hda3, here I use REDHAT7.2, the kernel is 2.4.7-10, the general file name is vmlinuz when using it, you can copy this kernel file or establish a connection when the system is normal. single means single use. root=/dev/hda3 is the location of the root of the Linux system. My computer is equipped with 98, if it only has Linux. It may be /dev/hda1. On the second hard disk, it is /dev/hdb1. Here is how Linux identifies partitions.

1.3GRUB method

This method is more complicated to boot. When entering the GRUB startup screen, press "C" to enter the GRUB command line. When you have a password, press "P "After that enter the password and then proceed to the GRUB command line.

Enter the following command on the command line to enable single user. I still use REDHAT7.2 as an example to illustrate kernel /boot/vmlinuz-2.4.7-10 single root=/dev/hda3initrd/boot/initrd -2.4.7-10.img boot (hd0,2) The first and second sentences indicate the kernel file. The keyword for single user is still single. Depending on the system, the file name may be different. The meaning of boot (hd0,2) is to boot from the third partition of the

first hard disk.

2. Methods to prevent single-user entry

Since a single user has complete control over the system, if the operation is improper or is entered by others, , then the consequences will be disastrous. How to prevent single users from entering the industry, there are the following aspects to pay attention to.

2.1 Protect the /etc/inittab file. If you change 3 in id:3:initdefault to 1, you can directly enter single-user mode every time you start. For the /etc/inittab file, just enter chown700 /etc/inittab as root and set the properties so that other users cannot modify it.

2.2 If you are using lilo to boot, you may set the waiting input time during boot to 0 or the shortest time through Linuxconf or directly modify lilo.conf. In this case, if you enter single-user mode, you can use a floppy disk to boot.

2.3 If you use GRUB to boot, the simplest method is to use the GRUB password to protect the startup options.

2.4 In order to prevent others from remotely damaging and restarting the system, in addition to effectively managing the ROOT password and files in the /etc directory, the CMOS password should also be set, so that even if the system is changed to Even in single-user mode, you cannot directly start the computer to operate.

ctrl x exit and enter single-user mode

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