/etc/apt/apt.conf.d/proxy.conf

Acquire {
  HTTP::proxy "http://proxy_server:port/";
  HTTPS::proxy "http://proxy_server:port/";
}

https://linuxiac.com/how-to-use-apt-with-proxy/

下面是 man apt-get 的摘录。使用 upgrade 时应遵守以下规则：在任何情况下都不得删除当前已安装的软件包，也不得检索和安装尚未安装的软件包。如果这对你很重要，那就用 apt-get upgrade。如果你想让一切 "正常运行"，你可能需要使用apt-get dist-upgrade来确保依赖关系得到解决。

upgrade

upgrade 用于从/etc/apt/sources.list 列举的源中安装系统当前安装的所有软件包的最新版本。当前安装的软件包如果有新版本可用，则会被检索和升级；在任何情况下，当前安装的软件包都不会被移除，尚未安装的软件包也不会被检索和安装。当前已安装的软件包的新版本，如果不能在不改变其他软件包安装状态的情况下升级，则会保留其当前版本。必须先进行更新，以便 apt-get 知道新版本的软件包可用。

dist-upgrade

除了执行升级功能外，dist-upgrade 还能智能地处理与新版本软件包的依赖关系变化；apt-get 有一个 "智能 "的冲突解决系统，它会尝试升级最重要的软件包，而命令可能会删除某些软件包。/etc/apt/sources.list文件包含一个位置列表，可以从中获取所需的软件包文件。另请参阅 apt_preferences(5)，了解覆盖个别软件包常规设置的机制。

deb http://deb.debian.org/debian bookworm main
deb-src http://deb.debian.org/debian bookworm main

deb http://deb.debian.org/debian-security/ bookworm-security main
deb-src http://deb.debian.org/debian-security/ bookworm-security main

deb http://deb.debian.org/debian bookworm-updates main
deb-src http://deb.debian.org/debian bookworm-updates main

Since the colors worked fine while being loggged in directly, I just un-uncommented the line force_color_prompt=yes in the file ~/.bashrc, that gave me colors over ssh, too:

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt
force_color_prompt=yes

(Ubuntu 18.04 LTS)

https://askubuntu.com/questions/16336/how-to-get-coloured-terminal-over-ssh

1. Install sudo. Some installations do not come with sudo installed. If your does not, install sudo with apt.

# apt install sudo

2. Create a new user account with the adduser command. Use a strong password for the new user. You can enter values for the user information, or press ENTER to leave those fields blank.

# adduser example_user
Adding user `example_user' ...
Adding new group `example_user' (1001) ...
Adding new user `example_user' (1001) with group `example_user' ...
Creating home directory `/home/example_user' ...
Copying files from `/etc/skel' ...
New password:
Retype new password:
passwd: password updated successfully
Changing the user information for example_user
Enter the new value, or press ENTER for the default
        Full Name []: Example User
        Room Number []:
        Work Phone []:
        Home Phone []:
        Other []:
Is the information correct? [Y/n] y

3. Add the new user to the sudo group.

# adduser example_user sudo

4. Test by switching to the new user.

# su - example_user

Verify you are the new user with whoami, then test sudo access with sudo whoami, which should return root.

$ whoami
example_user
$ sudo whoami
[sudo] password for example_user:
root

How to use Sudo on a Vultr Cloud Server