Ubuntu Error Modifying user group causes sudo command to be invalid

1. The hand has changed the current user's permission group, causes the sudo command to be unable to use, and the root user's password has not been modified, cannot login the root user.

2. Switch to Recoverymode and log in with the root user

3. Execute mount-o Rw,remount/command can modify file system to read and write

4. Then use the passwd command to change the root user password and restart

5.SU-command switch to root user

6. Modify the/etc/sudoers file to add the current user to root (all:all) =all Line

Kevin     (All:all) =all

Ubuntu Error Modifying user group causes sudo command to be invalid