November 03, 2021

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.)

Why?

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)¶

Minimum install
Update the current packages
```
# apt update
# apt upgrade
```
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/VBoxLinuxAdditions.run
```
5. Unmount the disk image and reboot
```
# eject
# reboot
```

Change the hostname if necessary

# sed -i 's/<CURRENT_HOSTNAME>/<NEW_HOSTNAME>/g' /etc/hosts
# echo '<NEW_HOSTNAME>' > /etc/hostname
# reboot

Enable the user to use 'sudo' command without password

Install sudo command
```
# apt install sudo
```

Setup sudo

# echo '<USERNAME>' 'ALL=(ALL:ALL)' 'NOPASSWD: ALL' > /etc/sudoers.d/<USERNAME>
# chomd 0440 /etc/sudoers.d/<USERNAME>

Make sure the user can use sudo command without password
```
# su - <USERNAME>
$ sudo env
```

logout

Setting up GUI (log in as a general user)¶

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'.)
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"