By default, UBUNTU starts the command line interface (tty1)

In graphic mode, first enter the terminal:
1. Run

Sudo Vim/etc/default/GRUB

2. Find

Grub_cmdline_linux_default = "quiet Splash"

3. Change

Grub_cmdline_linux_default = "quiet splash text"

(PS: Quiet indicates that the detailed startup process is not displayed; splash indicates that the progress bar is displayed)

4. Run

Sudo Update-grub

5. Reboot: the command line mode (tty1) can be started by default)
6. In command line mode, you must start the graphic mode and enter the following command:

Sudo startx

7. Return to command line mode in graphic mode. Press CTRL + ALT + F1 (tty1) and CTRL + C to disable the graphic mode.

 

8. Modify/etc/default/grub and return to the graphic interface.

Sudo Update-grub

When you restart the logon interface, enter the correct password. The password is only flashed and cannot enter the graphic interface. solution:

CTRL + ALT + F1 enter tty1, log on

Rm-RF ~ /. Xautheritysudo reboot