E: You Must Put Some 'deb-src' Uris In Your Sources.list

Fixing the "E: You Must Put Some 'deb-src' URIs in Your Sources.list" Error in Debian/Ubuntu

This error message, "E: You must put some 'deb-src' URIs in your sources.list," often pops up during package installations or updates in Debian-based systems like Ubuntu. It signifies that your system's /etc/apt/sources.list file is missing the necessary deb-src lines. This article explains what deb-src is, why it's needed, and how to resolve this error effectively.

What are deb and deb-src URIs?

When you install software using APT (Advanced Package Tool) in Debian or Ubuntu, you're essentially downloading packages from repositories specified in your /etc/apt/sources.list file. These repositories contain compiled binary packages (deb URIs). However, deb-src URIs point to the source code for those packages. This source code isn't typically necessary for basic installation, but it's crucial for specific tasks like:

• Building packages from source: This is essential if you need to compile a package with specific options or customizations not available in pre-built binaries.
• Debugging package issues: Having the source code allows you to inspect the codebase to identify and potentially fix problems within a package.
• Contributing to open-source projects: Accessing the source code allows you to participate in the development and improvement of the software.
• Advanced package management: Certain package management techniques and tools require access to the source code for their operation.

Why the Error Occurs

The "E: You must put some 'deb-src' URIs in your sources.list" error arises when you attempt an action (like building a kernel module, compiling a package from source using dpkg-buildpackage, or using certain debugging tools) that requires access to source code, but your /etc/apt/sources.list file lacks the corresponding deb-src entries. The system is simply telling you that it cannot find the source code repositories.

How to Solve the Error

The solution is straightforward: add deb-src lines to your /etc/apt/sources.list file. These lines should mirror your existing deb lines, but with deb-src instead of deb. Crucially, only add deb-src entries if you actually need them. Including them unnecessarily might increase download times and storage usage.

Here's how to do it:

1. Backup your sources.list: Before making any changes, create a backup of your /etc/apt/sources.list file:

   sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
   

2. Open sources.list: Use a text editor with root privileges to open the file:

   sudo nano /etc/apt/sources.list
   

3. Add deb-src lines: For every deb line, add a corresponding deb-src line directly beneath it. For example, if you have:

   deb http://archive.ubuntu.com/ubuntu focal main restricted universe multiverse
   

   Add the following line below it:

   deb-src http://archive.ubuntu.com/ubuntu focal main restricted universe multiverse
   

   Repeat this for all your deb entries.

4. Save and update: Save the changes and update your package lists:

   sudo apt update
   

This should resolve the "E: You must put some 'deb-src' URIs in your sources.list" error. Remember to only add deb-src entries when you need access to the source code for specific tasks. If the error persists after following these steps, consider checking for typos in your sources.list file or verifying your internet connection. Also ensure that the repositories you're referencing are still active and available.