取消 Ubuntu 圖形介面，改用文字介面

修改 GRUB

1. 修改 /etc/default/grub，將 GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" 變成 GRUB_CMDLINE_LINUX_DEFAULT="text"

   # If you change this file, run 'update-grub' afterwards to update
   # /boot/grub/grub.cfg.
   # For full documentation of the options in this file, see:
   #   info -f grub -n 'Simple configuration'
   
   GRUB_DEFAULT=0
   GRUB_HIDDEN_TIMEOUT=0
   GRUB_HIDDEN_TIMEOUT_QUIET=true
   GRUB_TIMEOUT=10
   GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
   #GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
   GRUB_CMDLINE_LINUX_DEFAULT="text"
   GRUB_CMDLINE_LINUX=""
   

2. 更新 GRUB

   root@cysrv:~# update-grub
   Generating grub configuration file ...
   Warning: Setting GRUB_TIMEOUT to a non-zero value when GRUB_HIDDEN_TIMEOUT is set is no longer supported.
   Found linux image: /boot/vmlinuz-4.4.0-63-generic
   Found initrd image: /boot/initrd.img-4.4.0-63-generic
   Found linux image: /boot/vmlinuz-4.4.0-62-generic
   Found initrd image: /boot/initrd.img-4.4.0-62-generic
   Found linux image: /boot/vmlinuz-4.4.0-59-generic
   Found initrd image: /boot/initrd.img-4.4.0-59-generic
   Found memtest86+ image: /memtest86+.elf
   Found memtest86+ image: /memtest86+.bin
   done
   

修改 systemd

1. sudo systemctl enable multi-user.target --force
2. sudo systemctl set-default multi-user.target

還原 GUI 設定 systemd 的方法

1. sudo systemctl unmask lightdm
2. sudo systemctl enable lightdm
3. sudo systemctl set-default graphical.target