Why does the `updatedb` program run so fast?












4














Usually when I have programs that are doing a full disk scan and going over all files in the system they take a very long time to run. Why does updatedb run so fast in comparison?






updatedb







share|improve this question



























    4














    Usually when I have programs that are doing a full disk scan and going over all files in the system they take a very long time to run. Why does updatedb run so fast in comparison?






    updatedb







    share|improve this question

























      4












      4








      4







      Usually when I have programs that are doing a full disk scan and going over all files in the system they take a very long time to run. Why does updatedb run so fast in comparison?






      updatedb







      share|improve this question













      Usually when I have programs that are doing a full disk scan and going over all files in the system they take a very long time to run. Why does updatedb run so fast in comparison?






      updatedb




      updatedb






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 1 hour ago









      hugomg

      1,66731632




      1,66731632






















          1 Answer
          1






          active

          oldest

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          5














          The answer depends on the version of locate you’re using, but there’s a fair chance it’s mlocate, whose updatedb runs quickly by avoiding doing full disk scans:




          mlocate is a locate/updatedb implementation. The 'm' stands for "merging":
          updatedb reuses the existing database to avoid rereading most of the file
          system, which makes updatedb faster and does not trash the system caches as
          much.




          (The database stores each directory’s timestamp, ctime or mtime, whichever is newer.)






          share|improve this answer























          • Fairly good question and answer, did not even know there were "differencial" scannings.
            – Rui F Ribeiro
            1 hour ago












          • Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
            – hugomg
            7 mins 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









          5














          The answer depends on the version of locate you’re using, but there’s a fair chance it’s mlocate, whose updatedb runs quickly by avoiding doing full disk scans:




          mlocate is a locate/updatedb implementation. The 'm' stands for "merging":
          updatedb reuses the existing database to avoid rereading most of the file
          system, which makes updatedb faster and does not trash the system caches as
          much.




          (The database stores each directory’s timestamp, ctime or mtime, whichever is newer.)






          share|improve this answer























          • Fairly good question and answer, did not even know there were "differencial" scannings.
            – Rui F Ribeiro
            1 hour ago












          • Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
            – hugomg
            7 mins ago
















          5














          The answer depends on the version of locate you’re using, but there’s a fair chance it’s mlocate, whose updatedb runs quickly by avoiding doing full disk scans:




          mlocate is a locate/updatedb implementation. The 'm' stands for "merging":
          updatedb reuses the existing database to avoid rereading most of the file
          system, which makes updatedb faster and does not trash the system caches as
          much.




          (The database stores each directory’s timestamp, ctime or mtime, whichever is newer.)






          share|improve this answer























          • Fairly good question and answer, did not even know there were "differencial" scannings.
            – Rui F Ribeiro
            1 hour ago












          • Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
            – hugomg
            7 mins ago














          5












          5








          5






          The answer depends on the version of locate you’re using, but there’s a fair chance it’s mlocate, whose updatedb runs quickly by avoiding doing full disk scans:




          mlocate is a locate/updatedb implementation. The 'm' stands for "merging":
          updatedb reuses the existing database to avoid rereading most of the file
          system, which makes updatedb faster and does not trash the system caches as
          much.




          (The database stores each directory’s timestamp, ctime or mtime, whichever is newer.)






          share|improve this answer














          The answer depends on the version of locate you’re using, but there’s a fair chance it’s mlocate, whose updatedb runs quickly by avoiding doing full disk scans:




          mlocate is a locate/updatedb implementation. The 'm' stands for "merging":
          updatedb reuses the existing database to avoid rereading most of the file
          system, which makes updatedb faster and does not trash the system caches as
          much.




          (The database stores each directory’s timestamp, ctime or mtime, whichever is newer.)







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 1 hour ago

























          answered 1 hour ago









          Stephen Kitt

          164k24365444




          164k24365444












          • Fairly good question and answer, did not even know there were "differencial" scannings.
            – Rui F Ribeiro
            1 hour ago












          • Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
            – hugomg
            7 mins ago


















          • Fairly good question and answer, did not even know there were "differencial" scannings.
            – Rui F Ribeiro
            1 hour ago












          • Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
            – hugomg
            7 mins ago
















          Fairly good question and answer, did not even know there were "differencial" scannings.
          – Rui F Ribeiro
          1 hour ago






          Fairly good question and answer, did not even know there were "differencial" scannings.
          – Rui F Ribeiro
          1 hour ago














          Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
          – hugomg
          7 mins ago




          Thanks! I had never noticed that modifying a file also changes the ctime and mtime of all its parent directories.
          – hugomg
          7 mins ago


















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