The solution steps are as follows:
1. When the grub screen appears, use the up/down key to select the item that you usually start Linux, and then press the e key;
2. Use the up and down keys again to select the one you usually start Linux (similar to kernel/boot/vmlinuz-2.4.18-14ro root = label =/), and then press the e key;
3. Modify the command line you see and add single. The result is as follows:
Kernel/boot/vmlinuz-2.4.18-14 single Ro root = label =/single
4. Press enter to return, and then press the B key to start, you can directly enter the Linux Command Line;
5. # vi/etc/shadow
Delete the contents of the first line, that is, the content before "root" and "Next", in the line starting with "root,
The first line is similar
Root ::......
Save and exit (WQ !).
6. You can also use the command passwd to change the password.
7. # restart reboot. the user name is root and the password is blank (no password is prompted) to log on.