How does apt/dpkg choose which real package is installed when a virtual package is specified as a dependency?












2














e.g. if package specifies 



Depends: www-browser


How does apt/dpkg decide which real package will be installed?






apt dpkg aptitude







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    2














    e.g. if package specifies 



    Depends: www-browser


    How does apt/dpkg decide which real package will be installed?






    apt dpkg aptitude







    share|improve this question



























      2












      2








      2







      e.g. if package specifies 



      Depends: www-browser


      How does apt/dpkg decide which real package will be installed?






      apt dpkg aptitude







      share|improve this question















      e.g. if package specifies 



      Depends: www-browser


      How does apt/dpkg decide which real package will be installed?






      apt dpkg aptitude




      apt dpkg aptitude






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 2 hours ago









      peterh

      4,28592957




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      asked 5 hours ago









      the_velour_fog

      5,24533360




      5,24533360






















          1 Answer
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          2














          According to this answer on Ask Ubuntu, apt will first try to install any non-virtual packages listed as options instead:




          Now, according to sources, apt tries first of satisfying the dependency before trying with virtual packages (i.e., if depends are firefox | www-browser, checks if any of the packages are installed, then try to install firefox if neither is).




          If not, it will simply iterate over the list of packages that provide the virtual one, and install the first one that it can:




          If the non-virtual package isn't available, it seems to just iterate over all packages which provides the virtual package, if no other dependencies are broken. Other comments evidence of this behavior are this which leads to GrpIterator::FindPreferredPkg function.







          share|improve this answer





















          • It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
            – Simon Richter
            1 hour ago











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          1 Answer
          1






          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          2














          According to this answer on Ask Ubuntu, apt will first try to install any non-virtual packages listed as options instead:




          Now, according to sources, apt tries first of satisfying the dependency before trying with virtual packages (i.e., if depends are firefox | www-browser, checks if any of the packages are installed, then try to install firefox if neither is).




          If not, it will simply iterate over the list of packages that provide the virtual one, and install the first one that it can:




          If the non-virtual package isn't available, it seems to just iterate over all packages which provides the virtual package, if no other dependencies are broken. Other comments evidence of this behavior are this which leads to GrpIterator::FindPreferredPkg function.







          share|improve this answer





















          • It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
            – Simon Richter
            1 hour ago
















          2














          According to this answer on Ask Ubuntu, apt will first try to install any non-virtual packages listed as options instead:




          Now, according to sources, apt tries first of satisfying the dependency before trying with virtual packages (i.e., if depends are firefox | www-browser, checks if any of the packages are installed, then try to install firefox if neither is).




          If not, it will simply iterate over the list of packages that provide the virtual one, and install the first one that it can:




          If the non-virtual package isn't available, it seems to just iterate over all packages which provides the virtual package, if no other dependencies are broken. Other comments evidence of this behavior are this which leads to GrpIterator::FindPreferredPkg function.







          share|improve this answer





















          • It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
            – Simon Richter
            1 hour ago














          2












          2








          2






          According to this answer on Ask Ubuntu, apt will first try to install any non-virtual packages listed as options instead:




          Now, according to sources, apt tries first of satisfying the dependency before trying with virtual packages (i.e., if depends are firefox | www-browser, checks if any of the packages are installed, then try to install firefox if neither is).




          If not, it will simply iterate over the list of packages that provide the virtual one, and install the first one that it can:




          If the non-virtual package isn't available, it seems to just iterate over all packages which provides the virtual package, if no other dependencies are broken. Other comments evidence of this behavior are this which leads to GrpIterator::FindPreferredPkg function.







          share|improve this answer












          According to this answer on Ask Ubuntu, apt will first try to install any non-virtual packages listed as options instead:




          Now, according to sources, apt tries first of satisfying the dependency before trying with virtual packages (i.e., if depends are firefox | www-browser, checks if any of the packages are installed, then try to install firefox if neither is).




          If not, it will simply iterate over the list of packages that provide the virtual one, and install the first one that it can:




          If the non-virtual package isn't available, it seems to just iterate over all packages which provides the virtual package, if no other dependencies are broken. Other comments evidence of this behavior are this which leads to GrpIterator::FindPreferredPkg function.








          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 5 hours ago









          Nonny Moose

          1415




          1415












          • It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
            – Simon Richter
            1 hour ago


















          • It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
            – Simon Richter
            1 hour ago
















          It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
          – Simon Richter
          1 hour ago




          It is discouraged to use pure virtual dependencies, usually you'd give one real and one virtual package as in your example. For Build-Depends, this is required by policy as well, as "or" relationships are ignored by autobuilders.
          – Simon Richter
          1 hour ago


















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