# How to set up a proxy server on Linux using Squid in 4 easy steps

Taking control of your network traffic creates a safer and faster browsing environment.

By setting up a Squid proxy server on Linux, you gain the power to filter content, cache data, and manage access with professional precision.


## The Importance of Network Proxies

In the modern digital landscape, direct connection to the internet poses various risks and management challenges. A proxy server serves as a buffer, a controlled gateway that manages the flow of information between internal clients and external web servers.

For system administrators, implementing a proxy is a fundamental step in securing a network infrastructure. It allows for the centralized application of security policies, making it easier to monitor usage and prevent unauthorized access to sensitive or distracting content.

**Squid** stands out as the solution of choice for Linux environments. It is a full-featured web proxy cache server that provides proxying and caching services for Hyper Text Transport Protocol (HTTP), File Transfer Protocol (FTP), and other popular network protocols.

## Step 1: Installation on Ubuntu/Debian

The installation process relies on the robust package managers found in Debian-based distributions. This ensures that the software is integrated correctly with the operating system.

### Updating the System

Before any installation, it is best practice to update the local package index. This ensures that the system retrieves the latest version of the software, including critical security patches.

Running an update minimizes the risk of compatibility issues and ensures that the server starts with a clean, secure slate.

### Installing Squid

The installation is executed via the command line. The package manager automatically resolves and installs all necessary dependencies required for Squid to function.

Once the installation completes, the service must be explicitly started and enabled. Enabling the service ensures that the proxy server restarts automatically after a system reboot, which is crucial for maintaining uninterrupted network service.

### Verifying the Service

Post-installation verification is a mandatory step. Administrators must check the status of the service to confirm it is active and running. This prevents troubleshooting configuration issues later that might actually be caused by a stopped service.

## Step 2: Configuration and Access Control

Out of the box, Squid is often configured to deny all connections for security reasons. Configuration involves defining who is allowed to use the resource.

### Defining Access Control Lists (ACLs)

Squid uses ACLs to identify traffic. The first step in configuration is defining an ACL that matches the local network's IP address range.

This definition effectively creates a group of trusted IP addresses. It does not grant access by itself, but it creates the label that will be used in the permission rules.

### Applying Permission Rules

Once the local network is defined, a rule must be added to allow traffic from that group. The order of rules in the Squid configuration file is critical.

Squid processes rules from top to bottom. The "allow" rule for the local network must be placed before the default "deny all" rule. If placed after, the traffic will be blocked before the permission rule is ever read.

### Port Security

Changing the default listening port is a recommended security hardening measure. Automated scanners frequently target standard ports.

By configuring Squid to listen on a non-standard port, administrators can reduce the visibility of the proxy to casual scanning, adding a layer of obscurity to the defense.

## Step 3: Advanced Features

Squid's true power lies in its advanced capabilities, which allow for granular control over network usage.

### User Authentication

Beyond simple IP-based restrictions, Squid supports user authentication. This requires users to enter a username and password to access the internet.

This is implemented by creating a password file and configuring Squid to check credentials against it. This feature is essential for environments where user accountability is required.

### Domain Blocking

Content filtering is a common requirement. Squid can be configured to read a list of prohibited domains from a text file.

Requests matching domains in this list are intercepted and denied. This mechanism is highly effective for enforcing corporate usage policies or parental controls.

### Caching Strategy

Caching configuration involves defining how much disk space Squid can use to store web objects.

When properly configured, Squid stores copies of visited pages. Subsequent requests for the same content are served from the disk rather than the internet, resulting in significant bandwidth savings and faster load times.

## Step 4: Client Configuration

The final phase involves directing network traffic from client devices through the newly configured proxy server.

### System-Wide Proxy Settings

Operating systems like Windows and macOS have centralized proxy configuration menus. Users simply need to input the IP address of the Linux server and the configured port.

This routes all HTTP and HTTPS traffic from the device through the Squid server, subjecting it to the defined filtering and caching rules.

### Command Line Integration

For Linux-based clients or servers, proxy settings are often handled via environment variables.

Exporting the proxy variables in the shell profile ensures that command-line tools respect the proxy settings, which is vital for maintaining security in automated environments.

All details here: https://safelyo.com/how-to-set-up-a-proxy-server-on-linux/

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