Enter single-user mode under CentOS7

Centos7 uses grub2, which is different from centos6.x's approach to single-user access. However, because it is a real machine environment, it cannot be captured, so it is only a rough description of the following ideas.

init method

1. Centos7's grub2 interface will have two entrances, normal system entrance and rescue mode;

2. Modify grub2 boot

Pressing "e" on the normal system entry will enter edit mode and search for the ro line, which starts with linux16;

Change ro to rw;(change read-only to writable)

Remove rhgb quiet;(quiet mode does not have code lines swishing away, can be deleted)

Add init=/bin/sh;(or init=/bin/bash, specify shell environment)

Press Ctrl+X to start the system.

3. Change the root password

#passwd #change password

#touch /.autorelabel #Selinux is said to update label after reboot

#exec /sbin/init #Start the init process normally

There is also a rd.break method (not tried)

1. When starting, press "e" on the corresponding startup item and kernel name in the startup interface;

After entering, find the beginning of Linux16, press the "end" key to the end, enter rd.break, press ctrl+x to enter;

3. After entering, enter the command mount, and find that the root is/sysroot/, and cannot be written, only ro=readonly permission;

mount -o mount,rw /sysroot/, mount again, then mount, found that you have r,w permissions;

5. chroot /sysroot/change root;

（1）echo redhat| passwd -stdin root Change the root password to redhat, or enter passwd and modify it interactively;

(2) There is also a cp first, and then modify the/etc/shadow file.

6, touch /.autorelabel This sentence is for selinux to take effect

7. Ctrl+D Exit

8 and then reboot.