Setting up proxy servers in Ubuntu can be done through multiple approaches, each serving different purposes and affecting different parts of the system. In this guide, we’ll explore all available methods, understand their differences, and learn how to configure proxy settings for specific applications.

Core Proxy Configuration Methods

1. Environment Variables in /etc/environment

The /etc/environment file is one of the most fundamental ways to set system-wide proxy settings. This file is read at boot time and affects all users on the system. When setting up your proxy, you’ll need to replace the port number (3128 in this example) with the specific port your proxy server uses.

http_proxy="http://proxy.example.com:3128"
https_proxy="http://proxy.example.com:3128"
ftp_proxy="http://proxy.example.com:3128"
no_proxy="localhost,127.0.0.1,::1"

HTTP_PROXY="http://proxy.example.com:3128"
HTTPS_PROXY="http://proxy.example.com:3128"
FTP_PROXY="http://proxy.example.com:3128"
NO_PROXY="localhost,127.0.0.1,::1"

The no_proxy variable is particularly important as it tells your system which addresses should bypass the proxy server. This includes localhost and your local network addresses, ensuring direct communication for internal resources.

Key characteristics:

• System-wide configuration affecting all users
• Loaded very early in the boot process
• Changes require a system reboot or re-login
• Both lowercase and uppercase variables are recommended for maximum compatibility

2. Profile Configuration in /etc/profile.d/

Creating a proxy configuration file in /etc/profile.d/ is another system-wide approach. This method offers better organization and easier maintenance compared to modifying /etc/profile directly.

# /etc/profile.d/proxy.sh
export http_proxy="http://proxy.example.com:3128"
export https_proxy="http://proxy.example.com:3128"
export ftp_proxy="http://proxy.example.com:3128"
export no_proxy="localhost,127.0.0.1,::1"

Key characteristics:

• Affects all users who use a shell
• Takes effect on new shell sessions
• More flexible than /etc/environment as it allows for script logic
• Changes apply after logging out and back in

3. User-Specific Configuration in ~/.bashrc

The ~/.bashrc method provides user-level proxy configuration, perfect when different users need different proxy settings:

# Add to ~/.bashrc
export http_proxy="http://proxy.example.com:3128"
export https_proxy="http://proxy.example.com:3128"
export ftp_proxy="http://proxy.example.com:3128"
export no_proxy="localhost,127.0.0.1,::1"

Key characteristics:

• Affects only the specific user
• Applied only to bash shell sessions
• Changes take effect in new terminal windows
• Ideal for user-specific proxy settings

4. GNOME/Ubuntu Settings GUI

For users who prefer a graphical interface, Ubuntu provides proxy settings through the System Settings application. You can find these settings by:

1. Opening Settings
2. Navigating to Network
3. Selecting Network Proxy
4. Choosing ‘Manual’ from the dropdown menu
5. Entering your proxy information in the provided fields

This method is particularly useful for users who are less comfortable with command-line configuration.

5. Apt Proxy Configuration

Apt has its own proxy configuration in /etc/apt/apt.conf.d/:

# /etc/apt/apt.conf.d/80proxy
Acquire::http::Proxy "http://proxy.example.com:3128";
Acquire::https::Proxy "http://proxy.example.com:3128";

Key characteristics:

• Specific to package management
• System-wide configuration
• Independent of other proxy settings
• Takes effect immediately

Application-Specific Proxy Settings

Different applications may require their own proxy configurations. You can verify your current proxy settings at any time by running:

env | grep -i proxy

wget

• Uses environment variables by default
• Can be configured in ~/.wgetrc:

  use_proxy=yes
  http_proxy=http://proxy.example.com:3128
  https_proxy=http://proxy.example.com:3128
  

curl

• Respects environment variables
• Can use command-line options:

  curl --proxy http://proxy.example.com:3128
  

git

• Configure proxy settings specifically for git:

  git config --global http.proxy http://proxy.example.com:3128
  git config --global https.proxy http://proxy.example.com:3128
  

Order of Precedence

Understanding how different proxy settings interact is crucial. They are typically applied in this order:

1. Command-line arguments (highest precedence)
2. Application-specific configuration
3. User-specific environment variables (~/.bashrc)
4. System-wide environment variables (/etc/environment)
5. Default settings (lowest precedence)

Conclusion

Ubuntu’s flexible proxy configuration system allows for both system-wide and user-specific settings. While this flexibility is powerful, it’s important to understand how different methods interact and choose the appropriate approach for your specific needs. For most users, a combination of /etc/environment for system-wide settings and application-specific configurations will provide the most reliable setup. Remember to always verify your settings using the env | grep -i proxy command after making changes.

Important Note About SSH Sessions and Proxy Settings

When working with remote systems through SSH, you might encounter a situation where proxy settings configured through Ubuntu’s graphical interface aren’t visible in your SSH session. This occurs because SSH sessions create a separate environment that doesn’t automatically inherit settings from the graphical user interface.

Think of this like having two different entrances to a building: the main entrance (graphical login) and a side door (SSH). Settings configured through the GUI are like instructions posted at the main entrance – they won’t be visible if you enter through the side door.

To ensure your proxy settings work consistently across both regular and SSH sessions, use one of these configuration methods on your remote system:

1. Add your proxy settings to /etc/environment:

   http_proxy="http://proxy.example.com:3128"
   https_proxy="http://proxy.example.com:3128"
   

2. Create a file in /etc/profile.d/proxy.sh:

   export http_proxy="http://proxy.example.com:3128"
   export https_proxy="http://proxy.example.com:3128"
   

3. Add the settings to the user’s ~/.bashrc:

   export http_proxy="http://proxy.example.com:3128"
   export https_proxy="http://proxy.example.com:3128"
   

After making these changes, your proxy settings will work consistently regardless of how you access the system. You can verify the settings are active in your SSH session by running:

env | grep -i proxy

This ensures that all applications requiring proxy access will work correctly, whether you’re accessing the system through a graphical session or SSH.