Note: Linux Proxy Settings

Proxy configuration on Linux.

Ref

Proxy server - ArchWiki
Environment variables - ArchWiki
These two docs basically cover most proxy-related issues on Linux.

How To Use Proxy Server To Access Internet at Shell Prompt With http_proxy Variable
This one is a simpler “just do it” guide.

I read a bunch of tutorials before and still didn’t get it.
In the end, good documentation is the most reliable.

2019/12/23 update

Set proxy via environment variables
Add to ~/.bashrc:

1
export http_proxy=http://<proxy_addr>:<proxy_port>/
2
export https_proxy=$http_proxy
3
export ftp_proxy=$http_proxy
4
export rsync_proxy=$http_proxy
5
export no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com"

Make sudo inherit proxy
Ref: Sudo Environment variables
Add to /etc/sudoers:

1
Defaults env_keep += "ftp_proxy http_proxy https_proxy no_proxy"

2021/02/24 update
It’s better not to edit sudoers directly. Add a file under /etc/sudoers.d/ instead.

1
$ sudo visudo /etc/sudoers.d/env_proxy
2

3
 Add following line
4
Defaults env_keep += "ftp_proxy http_proxy https_proxy no_proxy"

Ref:adding local content in /etc/sudoers.d/ instead of directly modifying sodoers file via visudo

2021/05/09 update

1
 vim /etc/sudoers.d/05_proxy
2

3
Defaults env_keep += "*_proxy *_PROXY"

Ref: ArchWiki - Proxy server: Keep proxy through sudo

Snap downloads via proxy
Ref: How to install snap packages behind web proxy on Ubuntu 16.04
Run:

1
sudo snap set system proxy.http="http://<proxy_addr>:<proxy_port>"
2
sudo snap set system proxy.https="http://<proxy_addr>:<proxy_port>"

Ubuntu: sudo inherit proxy
Ref: How to keep environment variables when using sudo
Ubuntu seems a bit different: you can’t put multiple variables on one line.

1
sudo visudo
2

3
 For Ubuntu 14, you need to specify in separate lines as it returns the errors for multi-variable lines:
4
Defaults  env_keep += "http_proxy"
5
Defaults  env_keep += "https_proxy"
6
Defaults  env_keep += "HTTP_PROXY"
7
Defaults  env_keep += "HTTPS_PROXY"

2021/04/10 update

curl and pacman

Ref: ArchWiki - Proxy server: crul and pacman

You may set the all_proxy environment variable to let curl and pacman (which uses curl) use your socks5 proxy:
$ export all_proxy="socks5://your.proxy:1080"