How to Fix "W: Some index files failed to download." Error In Ubuntu?


When you are running updates on Ubuntu, you may come across an error message that says "Some index files failed to download". This error occurs when Ubuntu is unable to download the package indexes from the software repositories it relies on for updates. The package indexes contain a list of available packages, their versions, and dependencies.

Without these indexes, you cannot update or install new packages on your system. It is important to fix this error as soon as possible because it can cause your system to be vulnerable to security risks and bugs.

Additionally, if you do not fix this error, you may experience issues when trying to install new packages or updates in the future. Therefore, in this article, we will guide you through the steps necessary to fix this error and ensure that your system remains up-to-date and secure.

Understanding the Error

Causes of the Error

The "Some index files failed to download" error in Ubuntu can be caused by various issues. One of the most common causes is network connectivity problems. This occurs when your computer fails to establish a connection with Ubuntu's servers.

Network connectivity problems are often caused by unstable internet connections or DNS configuration issues. Another cause of this error is software sources issues.

Software sources are repositories that contain all the necessary packages and updates for your Ubuntu system. If there is an issue with any of these repositories, it can cause errors during package installation or updates.

Proxy servers can also cause this error in Ubuntu systems. Proxy server issues usually occur when you are using a proxy server to access the internet and it's not configured properly.

Symptoms of the Error

When you encounter this error, you will see an error message that says "Some index files failed to download." This message indicates that there was an issue during package installation or update. You may also notice that some packages fail to install or update because of this error.

In some cases, you may experience slow internet speeds, which could indicate network connectivity issues. Additionally, if your software sources contain faulty repositories, you may notice package management errors such as dependency conflicts or missing packages.

Fixing the Error

Now that we understand what causes the "Some index files failed to download" error in Ubuntu and its symptoms, let us delve into the solutions. Luckily, fixing this issue is not as complicated as it may seem. Here are some steps you can take to resolve the error −

Checking network connectivity

The first step towards fixing this error is to ensure that your internet connection is stable and functioning correctly. Often, intermittent or slow network connections can hamper package downloads and cause "Some index files failed to download" errors.

Verifying internet connection

You can verify your internet connection using various methods such as opening a web browser and accessing a website or pinging a remote server from the terminal. If your network connection is broken, try resetting it by unplugging and plugging back in your modem or router.

Checking DNS settings

If you are sure that your network connection is working but still experiencing issues downloading packages, it could be because of incorrect DNS settings. You can check if your DNS settings are correct by running the following command in the terminal −

$ ping 

If the above command fails with a message indicating an unknown host or similar errors, then you should look into changing your DNS settings.

Disabling VPN or proxy servers

If you are connecting to the internet through VPN or proxy servers, try disabling them temporarily during package downloads to see if they are causing issues with downloading packages.

Updating software sources

If checking for network connectivity did not solve “Some index files failed to download” error; then updating software sources might help resolve it. Sometimes software sources become outdated causing errors when trying to download packages. You can update software sources by removing faulty sources and adding new repositories.

Removing faulty sources

To remove a faulty source, you need to open the Software & Updates application.

  • Click on the “Other Software” tab.

  • Select the repository that is causing errors and click on “Remove”.

  • Once removed, click on “Close” to save changes.

Adding new repositories

To add a new repository, you need to open the terminal and run −

$ sudo add-apt-repository ppa:

The above command will add the specified repository's PPA (Personal Package Archive) to your system's software sources list.

Once added, you can update your system's package lists by running −

$ sudo apt-get update 

Clearing cache and updating packages

If all else fails, clearing your cache and updating packages might help in resolving this error. You can clear your cache with the following command −

$ sudo apt-get clean 

This command clears out cached .deb files from /var/cache/apt/archives/ which might be corrupt or out of date. Once done, update your packages list by running −

$ sudo apt-get update 

This step will ensure that your package lists are up-to-date with any changes you made in software sources

You can then upgrade all installed packages with −

$ sudo apt-get upgrade 

Troubleshooting Tips for Persistent Errors

While the steps outlined in section III should fix most "Some index files failed to download" errors, sometimes the issue persists even after going through all of them. In such cases, here are some additional troubleshooting steps that can help resolve the issue −

Checking Firewall Settings

A firewall is a software or hardware system that helps protect your computer against unauthorized access. However, it can sometimes interfere with Ubuntu's software updates.

If you suspect that your firewall is causing the error, you can try temporarily disabling it and see if that fixes the issue. To disable your firewall, open your terminal and type −

sudo ufw disable

If this fixes the error, then you may need to configure your firewall to allow Ubuntu's software updates.

Resetting Network Configurations

If you're still experiencing the error even after disabling your firewall, resetting network configurations on your Ubuntu computer may help resolve the issue. To do this −

  • Open Terminal by pressing Ctrl + Alt + T keys together.

  • Type in: sudo /etc/init.d/networking restart and hit Enter.

  • This should reset all network configurations and refresh any stale connections or configurations.

Disabling IPv6

In rare cases, disabling IPv6 (Internet Protocol version 6) might help resolve persistent "Some index files failed to download" errors in Ubuntu. To disable IPv6 −

  • Open Terminal by pressing Ctrl+Alt+T keys together.

  • Type in: sudo nano /etc/sysctl.conf. This will open a new file for editing using Nano text editor.

  • Add the following lines to the bottom of the file −

net.ipv6.conf.default.disable_ipv6=1 net.ipv6.conf.lo.disable_ipv6=1
  • Save and exit by pressing Ctrl+X, Y, and Enter.

After completing any of these troubleshooting tips, you should repeat the steps outlined in section III to update your software sources and upgrade packages.


In this article, we have discussed the "Some index files failed to download" error in Ubuntu. We have learned that this error occurs due to network issues, software sources issues, and proxy server issues.

To fix the issue, we need to check our network connectivity, update software sources, clear cache and update packages. We have also provided some troubleshooting tips for persistent errors.

Ubuntu is a robust operating system that is designed to be secure and stable. However, like any other operating system, it requires regular maintenance to keep it running smoothly.

Updated on: 05-Jun-2023

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