Some sources can be modernized. Run ‘apt modernize-sources’ to do so

Thanks to Alan Pope that explained so clearly the Run ‘apt modernize-sources’ to do so issue at discourse.ubuntu.com:

The notice “Some sources can be modernized. Run ‘apt modernize-sources’ to do so” appears because your Ubuntu system has detected software repository configurations using the older, traditional format (.list files, typically /etc/apt/sources.list and files in /etc/apt/sources.list.d/).

Ubuntu (and Debian) are transitioning to a newer, more structured format called “deb822” using .sources files (usually placed in /etc/apt/sources.list.d/). This format is generally considered more readable, less prone to certain types of errors, and easier for tools to parse.

The apt modernize-sources command is a helper tool provided to automatically convert your existing .list files into the new .sources format.

There isn’t a specific configuration option within apt designed solely to turn off only this modernization notice while keeping the old .list files active. The notice is there specifically because the condition (presence of .list files) exists.

Therefore, the primary ways to stop seeing the notice are:

• Run the Modernization Command (Recommended):
  • This is the intended solution. Running sudo apt modernize-sources will analyze your existing .list files and attempt to convert them into the new .sources format.
  • It typically backs up your old configuration files before making changes (e.g., adding a .bak extension or similar).
  • Once your sources are successfully converted and the old .list files are no longer the primary configuration (they might be commented out or removed by the tool), apt will no longer detect sources needing modernization, and the notice will disappear.
  • Before running: It’s always wise to manually back up your /etc/apt/sources.list file and the contents of the /etc/apt/sources.list.d/ directory, just in case something unexpected happens during the conversion.

sudo cp /etc/apt/sources.list /etc/apt/sources.list.backup
sudo cp -R /etc/apt/sources.list.d/ /etc/apt/sources.list.d.backup

Then run the modernization:

sudo apt modernize-sources

After running it, test with sudo apt update to ensure everything still works correctly.

• Use Quiet Flags (Not Ideal for Suppressing Just This):

The best and intended way to “suppress” the notice is to address the underlying reason it’s appearing: run sudo apt modernize-sources to convert your repository configuration files to the newer format. While you can technically ignore the notice and continue using the .list files (they still work), the notice will likely persist until you modernize or use general quiet flags that hide other output too. Modernizing is generally safe and aligns with the direction the distribution is heading.