Ubuntu – How to fix “W: Duplicate sources.list entry”

aptconfigurationsoftware-sources

I keep getting this warning whenever I try to run sudo apt-get update.

W: Duplicate sources.list entry http://archive.ubuntu.com/ubuntu/ precise-updates/main i386 Packages (/var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_precise-updates_main_binary-i386_Packages)
W: You may want to run apt-get update to correct these problems

Below is the output from /etc/apt/sources.list file:

deb http://archive.ubuntu.com/ubuntu precise main restricted
deb-src http://archive.ubuntu.com/ubuntu precise main restricted

deb http://archive.ubuntu.com/ubuntu precise-updates main restricted
deb-src http://archive.ubuntu.com/ubuntu precise-updates main restricted

deb http://archive.ubuntu.com/ubuntu precise universe
deb-src http://archive.ubuntu.com/ubuntu precise universe
deb http://archive.ubuntu.com/ubuntu precise-updates universe
deb-src http://archive.ubuntu.com/ubuntu precise-updates universe

deb http://archive.ubuntu.com/ubuntu precise multiverse
deb-src http://archive.ubuntu.com/ubuntu precise multiverse
deb http://archive.ubuntu.com/ubuntu precise-updates multiverse
deb-src http://archive.ubuntu.com/ubuntu precise-updates multiverse

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

How do I fix it?

Best Answer

  • Your sources.list really has duplicate entries.

    First Let's see the correct form of a repository line or source line:

    The correct format of repository source line is

    <type of repository>  <location>  <dist-name> <components> 
    

    For example, a repo line can be like this one

      deb http://archive.ubuntu.com/ubuntu precise main
    

    Here, it means, the repository is for binary packages, which are hosted in http://archive.ubuntu.com/ubuntu and this repository is for Ubuntu precise (12.04) and this repository contains the main (software which are officially supported by Canonical) component.

    • Type: The type can be deb and deb-src. deb means a binary repository where deb-src means a source repository

    • Location: http://archive.ubuntu.com/ubuntu location of the repository.

    • Dist-name: The distribution name of Ubuntu release. For Ubuntu 12.04 it is precise, for 11.10 it is oneiric.
      You can visit the Ubuntu Wiki to view an updated list of Ubuntu releases and their code names.

    • Component: It can be main, universe, multiverse and restricted. These words indicates the level of supports for the packages and the licensing status.

    See this page for more information.

    Please take note that, you can add one or more component in a line, so "main", "universe", "restricted" and "multiverse" can be in a single line. Also note, Though you add more than one component in a single line, APT system considers them as separate line containing only one component.

    So, If your sources.list have a line like this

    deb http://archive.ubuntu.com/ubuntu precise universe
    

    Then it can't have another line like the below (which your files have)

    deb http://archive.ubuntu.com/ubuntu precise main universe
    

    which is equivalent of these two lines

    deb http://archive.ubuntu.com/ubuntu precise main
    deb http://archive.ubuntu.com/ubuntu precise universe
    

    Because, you are duplicating universe twice, so there will be an error for that duplicate. An error will be given for each duplicate found.

    Solution:

    After analyzing your sources.list file, I found that, It is a basic one which is supplied by Ubuntu by default. You can build a default file following the procedure:

    1. Open a terminal and first rename the existing sources.list file to sources.list.bak file. (we can safely remove that, but caution is good).

       sudo mv /etc/apt/sources.list /etc/apt/sources.list.bak
      
    2. Then open software-properties-gtk to build a new one. Type the below command in a terminal or in dash command prompt with pressing Alt+F2

      software-properties-gtk
      

      Note, for Ubuntu version 11.10 or earlier you have to use gksu before the software-properties-gtk command

    3. After the window is open,

      • Select all four categories in Ubuntu Software tab
      • Select precise-security, precise-updates and precise-backports category in Updates tab.
      • Select Canonical partner and Independent category from Other software tab.

    That's it. You have now a default sources.list file without error. Compare this file with the previous one, if you want.


    Update to deal with sources.list.d dir's files

    Sometimes a duplicate entry can be in a file in the /etc/apt/sources.list.d directory, which is also used by APT. So, you should look at that directory and see if there is any duplicate in those files. It is not necessary for duplicates being in the same file.

    Example case:

    A user had this error message showing while doing sudo apt-get update.

    W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main amd64 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-amd64_Packages)
    W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main i386 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-i386_Packages)
    W: You may want to run apt-get update to correct these problems
    

    But there was no entry with http://dl.google.com in the main /etc/apt/sources.list file. Looking at the /etc/apt/sources.list.d/ directory we found these files:

    output of ls /etc/apt/sources.list.d/:

    aims-sagemath-precise.list
    aims-sagemath-precise.list.save
    dropbox.list
    dropbox.list.save
    fossfreedom-packagefixes-precise.list
    fossfreedom-packagefixes-precise.list.save
    google-chrome.list
    google-chrome.list.save
    google.list
    google.list.save
    sagemath-monolithic-precise.list
    sagemath-monolithic-precise.list.save
    

    The files google-chrome.list and google.list were good candidates for containing duplicates. So, checking the contents of both files was necessary.

    Output of cat /etc/apt/sources.list.d/google-chrome.list:

    deb http://dl.google.com/linux/chrome/deb/ stable main  
    

    and of cat /etc/apt/sources.list.d/google.list

    deb http://dl.google.com/linux/chrome/deb/ stable main
    

    So, there was a duplicate entries in the sources of Apt. Since google-chrome.list only contain a single apt line and it was also listed in google.list file we can safely remove this file with the command

    sudo rm /etc/apt/sources.list.d/google-chrome.list
    

    Then the problem was solved.