November 03, 2021

English | 日本語

Setup GUI for Debian Bullseye (English)

Memo how to set up GUI for Debian Bullseye.

btw, they said that we should not log in as a root, because it may destroy the OS by mistake. We can acquire the root privilege using the command ‘sudo’ when necessary.

For example, an infinite loop to append to a file. Usually, the user cannot use the disk fully, so it causes an error and stops before running out of disk space.

In the case of root user, however, such a loop will consume all. Then, the OS may stop working, and possibly it might not boot after that.

I know that, however, I make it a rule to log in as a root at the first setting. (settings for network, hostname, and sudo command.)


First, I may not acquire the root privilege after some mistake. It is impossible to recover after that unless we log in as a root.

Next, I could reinstall the OS if I would ruin the OS. We should not be afraid of trouble too much before starting to use it. (That’s why I don’t use the command ‘visudo’ at the first step.)

So I log in as a root at first.

Initial Setup (log in as a root)

  1. Minimum install

  2. Update the current packages

    # apt update
    # apt upgrade
  3. Install “Guest Additions” in case of VirtualBox

    1. Insert the image of “Guest Additions”

    2. Mount the image

      # mount /media/cdrom0
    3. Install the build dependencies

      # apt install linux-headers-amd64 make perl gcc bzip2
    4. Build and install Guest Additions

      # sh /media/cdrom0/
    5. Unmount the disk image and reboot

      # eject
      # reboot
  4. Change the hostname if necessary

    # sed -i 's/<CURRENT_HOSTNAME>/<NEW_HOSTNAME>/g' /etc/hosts
    # echo '<NEW_HOSTNAME>' > /etc/hostname
    # reboot
  5. Enable the user to use ‘sudo’ command without password

    1. Install sudo command

      # apt install sudo
    2. Setup sudo

      # echo '<USERNAME>' 'ALL=(ALL:ALL)' 'NOPASSWD: ALL' > /etc/sudoers.d/<USERNAME>
      # chomd 0440 /etc/sudoers.d/<USERNAME>
    3. Make sure the user can use sudo command without password

      # su - <USERNAME>
      $ sudo env
  6. logout

Setting up GUI (log in as a general user)

  1. Install gnome

    $ sudo apt install task-gnome-desktop
    $ sudo reboot

    (In case of Ubuntu 20.04, install ‘ubuntu-genome-desktop’ instead of ‘task-gnome-desktop’.)

  2. Setup Japanese input

    1. Install mozc

      $ sudo apt install fcitx5-mozc

    (In case of Ubuntu 20.04, install ‘fcitx-mozc’ instead of ‘fcitx5-mozc’.)

    1. Change “Alternate Characters Key” if necessary

      Settings -> Keyboard Shortcuts -> “Alternate Characters Key”

    2. Disable the shortcut to “Switch windows of an application” (It is not compatible with changing input method key.)

      Settings -> Keyboard Shortcuts -> “Switch windows of an application”

      It is a good idea to search in “Keybord Shortcuts” view.
    3. Setup fcitx5

      1. Start fcitx5

      2. Select “mozc” from “Available Input Method:” and append to “Current Input Method” in “Input Method” tab

      3. Delete all from “Trigger Input Method” and add “Alt + `” to it in “Global Options” tab

    4. Select fcitx5 as input method
      Open “Input Method” and select “fcitx5”