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In /etc/apt/sources.list.d I have several files for custom repositories. All the names of those files end with .list.

Is it obligatory that files in that folder should end with that extension? If yes, where is that information written?

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up vote 13 down vote accepted

Yes, names of files in /etc/sources.list.d must end in .list for lines in the files to be taken as specifying software sources that ought to be used. Otherwise, the files may be taken to have a different meaning.


From man sources.list (1):

NAME sources.list - Package resource list for APT


The package resource list is used to locate archives of the package distribution system in use on the system. At this time, this manual page documents only the packaging system used by the Debian GNU/Linux system. This control file is /etc/apt/sources.list.

The source list is designed to support any number of active sources and a variety of source media. The file lists one source per line, with the most preferred source listed first. The format of each line is: type uri args The first item, type determines the format for args. uri is a Universal Resource Identifier (URI), which is a superset of the more specific and well-known Universal Resource Locator, or URL. The rest of the line can be marked as a comment by using a #.


The /etc/apt/sources.list.d directory provides a way to add sources.list entries in separate files. The format is the same as for the regular sources.list file. File names need to end with .list and may only contain letters (a-z and A-Z), digits (0-9), underscore (_), hyphen (-) and period (.) characters. Otherwise APT will print a notice that it has ignored a file if the file doesn't match a pattern in the Dir::Ignore-Files-Silently configuration list - in this case it will be silently ignored...


The .list.save files are some kind of work/backup files:


  1. http://manpages.ubuntu.com/
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You have not mentioned the problem you are having. But to answer your query there has to be two files at /etc/apt/sources.list.d/ for every repository, one will end with *.list and other *.list.save. But you don't have to play with them as repositories are added to /etc/apt/sources.list.

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I'm not solving any particular problem, I'm just learning how repositories are working in ubuntu. I don't understand why there should 2 files (with the exact content) and why not to use them to add repos. –  bessarabov Nov 26 '11 at 8:35
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