1. 开机按Esc，进入GRUB
  2. 选择*Advanced options for Ubuntu
  3. 选择*Ubuntu,with Linux 4.15.0-20-generic(recovery mode)
  4. 选择root drop to root shell promt
  5. mount -o remount,rw /ect
  6. chattr -i ect/passwd
  7. lasttr -v erc/passwd
  8. passwd
  9. 输入新密码
  10. 再次输入新密码
  11. passwd: password updated successfully