Debian Proxy Settings

In many network environments, especially corporate or educational settings, direct internet access might be restricted. Instead, traffic must pass through a proxy server that acts as an intermediary between your Debian system and the wider internet. This guide will help you understand and configure proxy settings correctly in Debian.

What is a Proxy Server?

A proxy server functions as an intermediary between your computer and the internet. When you configure proxy settings in Debian, you're essentially telling your system to route specific types of network traffic through this intermediary server.

Common reasons for using a proxy:

• Security: Proxies can filter malicious content
• Access control: Organizations can restrict access to certain websites
• Privacy: Your direct IP address is hidden from websites you visit
• Caching: Proxies can cache frequently accessed content to improve speed
• Bypassing geo-restrictions: Access content that might be restricted in your region

Environment Variables for Proxy Settings

The most universal way to configure proxy settings in Debian is through environment variables. These variables are used by most applications to determine how to connect to the internet.

Main Proxy Environment Variables

bash

# HTTP proxy
export http_proxy="http://proxy.example.com:8080"

# HTTPS proxy
export https_proxy="http://proxy.example.com:8080"

# FTP proxy
export ftp_proxy="http://proxy.example.com:8080"

# No proxy - domains that should bypass the proxy
export no_proxy="localhost,127.0.0.1,local.home"

Setting Proxy Variables Temporarily

To set proxy settings for your current terminal session only:

bash

export http_proxy="http://proxy.example.com:8080"
export https_proxy="http://proxy.example.com:8080"

You can verify the settings are active by echoing the variables:

bash

echo $http_proxy

Output:

http://proxy.example.com:8080

Setting Proxy Variables Permanently

To make proxy settings permanent for a user, add the export commands to your ~/.bashrc or ~/.profile file:

bash

# Open your profile file
nano ~/.profile

# Add these lines to the file
export http_proxy="http://proxy.example.com:8080"
export https_proxy="http://proxy.example.com:8080"
export ftp_proxy="http://proxy.example.com:8080"
export no_proxy="localhost,127.0.0.1,local.home"

# Save and close the file (Ctrl+O, Enter, Ctrl+X)

Apply the changes immediately:

bash

source ~/.profile

For system-wide proxy settings, you can add these export commands to /etc/environment or create a file in /etc/profile.d/:

bash

# Create a proxy settings file
sudo nano /etc/profile.d/proxy.sh

# Add proxy settings
export http_proxy="http://proxy.example.com:8080"
export https_proxy="http://proxy.example.com:8080"
export ftp_proxy="http://proxy.example.com:8080"
export no_proxy="localhost,127.0.0.1,local.home"

# Save and make it executable
sudo chmod +x /etc/profile.d/proxy.sh

Authentication with Proxy Servers

If your proxy requires authentication, include the username and password in the URL:

bash

export http_proxy="http://username:[email protected]:8080"
export https_proxy="http://username:[email protected]:8080"

Note: Storing passwords in plain text files is a security risk. Consider using a more secure method for sensitive environments.

Configuring APT to Use a Proxy

The Advanced Package Tool (APT) is Debian's package management system. You can configure it to use a proxy in several ways:

Method 1: Using apt.conf

Create or edit the apt.conf file:

bash

sudo nano /etc/apt/apt.conf

Add the following lines:

Acquire::http::Proxy "http://proxy.example.com:8080";
Acquire::https::Proxy "http://proxy.example.com:8080";

Method 2: Using apt.conf.d directory

Create a new file in the apt.conf.d directory:

bash

sudo nano /etc/apt/apt.conf.d/90proxy

Add the proxy configuration:

Acquire::http::Proxy "http://proxy.example.com:8080";
Acquire::https::Proxy "http://proxy.example.com:8080";

Method 3: Temporary APT proxy for a single command

You can also set a proxy for a single APT command:

bash

sudo apt-get -o Acquire::http::Proxy="http://proxy.example.com:8080" update

Configuring Git to Use a Proxy

If you use Git on your Debian system, you can configure it to use a proxy:

bash

# For HTTP
git config --global http.proxy http://proxy.example.com:8080

# For HTTPS
git config --global https.proxy http://proxy.example.com:8080

To verify the settings:

bash

git config --get http.proxy

Output:

http://proxy.example.com:8080

To remove the proxy settings:

bash

git config --global --unset http.proxy
git config --global --unset https.proxy

Configuring wget to Use a Proxy

The file ~/.wgetrc can be used to configure proxy settings for wget:

bash

# Create or edit .wgetrc
nano ~/.wgetrc

# Add these lines
http_proxy = http://proxy.example.com:8080
https_proxy = http://proxy.example.com:8080

Configuring cURL to Use a Proxy

For cURL, you can set proxy settings in the ~/.curlrc file:

bash

# Create or edit .curlrc
nano ~/.curlrc

# Add proxy configuration
proxy = "http://proxy.example.com:8080"

Using Desktop Environment Proxy Settings

If you're using a desktop environment like GNOME or KDE, you can also configure proxy settings through the GUI:

GNOME Desktop Environment

1. Go to Settings > Network
2. Click on Network Proxy
3. Choose "Manual" from the dropdown menu
4. Enter your proxy details for HTTP, HTTPS, FTP, and SOCKS
5. Click "Apply"

KDE Desktop Environment

1. Go to System Settings > Network > Proxy
2. Select "Manual Proxy Configuration"
3. Enter your proxy details
4. Click "Apply"

Testing Your Proxy Configuration

After setting up your proxy, it's important to test if it's working correctly:

Using curl to test HTTP proxy:

bash

curl -I http://www.example.com

If configured correctly, you should see a successful HTTP response.

Check your external IP address:

bash

curl http://ifconfig.me

The output should show the IP address of your proxy server, not your direct connection.

Testing APT with proxy:

bash

sudo apt update

If the update runs without network errors, your APT proxy configuration is working.

Troubleshooting Proxy Issues

Problem: Unable to connect through proxy

Solution: Verify proxy address and port:

bash

ping proxy.example.com
telnet proxy.example.com 8080

Problem: Authentication failures

Solution: Double-check username and password in the proxy URL.

Problem: Some applications still not using proxy

Solution: Some applications have their own proxy settings. Check application-specific documentation.

Problem: Proxy settings work for some protocols but not others

Solution: Ensure you've set proxy variables for all required protocols (HTTP, HTTPS, FTP).

Common Patterns and Best Practices

1. Use a proxy configuration script: For complex environments, consider using a script to manage proxy settings.

   bash

   #!/bin/bash
   # proxy-on.sh
   export http_proxy="http://proxy.example.com:8080"
   export https_proxy="http://proxy.example.com:8080"
   export ftp_proxy="http://proxy.example.com:8080"
   export no_proxy="localhost,127.0.0.1,local.home"
   echo "Proxy environment variables set."

   bash

   #!/bin/bash
   # proxy-off.sh
   unset http_proxy
   unset https_proxy
   unset ftp_proxy
   unset no_proxy
   echo "Proxy environment variables removed."

2. Consider security: Avoid storing plain-text passwords in proxy URLs when possible. Use environment variables for sensitive information.

3. Document your settings: Keep track of your proxy configuration for future reference.

Summary

Configuring proxy settings in Debian is essential when working in environments where direct internet access is restricted. In this guide, we've covered:

• Understanding what a proxy server is and why it's used
• Setting up environment variables for proxy configuration
• Configuring specific applications like APT, Git, wget, and cURL
• Setting up desktop environment proxy settings
• Testing and troubleshooting proxy configurations

By following these instructions, you should be able to successfully configure proxy settings on your Debian system, allowing it to communicate effectively with the internet through your organization's proxy infrastructure.

Additional Resources

• Debian Wiki: AptConf
• Debian Manual: APT
• Environment Variables in Linux

Exercises

1. Configure proxy settings for your Debian system using environment variables and test the connection using curl.
2. Set up APT to use a proxy and install a new package to verify it works.
3. Create shell scripts to quickly enable and disable proxy settings.
4. Configure Git to use a proxy and clone a repository to test the connection.