Frequently Asked Questions

rmlint finds more/less dupes than tool X!

Make sure that none of the following applies to you:

Both tools might investigate a different number of files. rmlint e.g. does not look through hidden files by default, while other tools might follow symlinks by default. Suspicious options you should look into are:

  • --hidden: Disabled by default, since it might screw up .git/ and similar directories.
  • --hardlinked: Might find larger amount files, but not more lint itself.
  • --followlinks: Might lead rmlint to different places on the filesystem.
  • --merge-directories: pulls in both --hidden and --hardlinked.

If there's still a difference, check with another algorithm. In particular use -pp to enable paranoid mode. Also make sure to have -D (--merge-directories) disabled to see the raw number of duplicate files.

Still here? Maybe talk to us on the issue tracker.

Can you implement feature X?

Depends. Go to to the issue tracker and open a feature request.

Here is a list of features where you probably have no chance:

  • Port it to Windows.
  • Find similar files like ssdeep does.

I forgot to add some options before running on a large dataset. Do I need to re-run it?

Probably not. Since rmlint 2.3.0 there is --replay which can be used to to re-output a json file of a prior run.

If you have changed the filesystem that might not be a good idea of course. In this case you'll have to re-run, but it's not as bad as it sounds though. Your filesystem is probably very good at caching.

If you only want to see the difference to what changed since last time you can look into -n --newer-than-stamp / -N --newer-than.

Still there are some cases where re-running might take a long time, like running on network mounts. By default, rmlint writes a rmlint.json file along the This can be used to speed up the next run by passing it to --cache. It should be noted that using the cache file for later runs is discouraged since false positives will get likely if the data is changed in between. Therefore there will never be an "auto-pickup" of the cache file.

I have a very large number of files and I run out of memory and patience.

As a rule of thumb, rmlint will allocate ~150 bytes for every file it will investigate. Additionally paths are stored in a patricia trie, which will compress paths and save memory therefore.

The memory peak is usually shortly after it finished traversing all files. For example, 5 million files will result in a memory footprint of roughly 1.0GB of memory in average.

If that's still not enough read on.

Some things to consider:

  • Use --with-metadata-cache to swap paths to disk. When needed the path is selected from disk instead of keeping them all in memory. This lowers the memory footprint per file by a few bytes. Sometimes the difference may be very subtle since all paths in rmlint are stored by common prefix, i.e. for long but mostly identically paths the point after the difference is stored.

    This option will most likely only make sense if you files with long basenames. You might expect 10%-20% less memory as a rule of thumb.

  • Enable the progress bar with -g to keep track of how much data is left to scan.


  • Some options like -D will not work well with --with-metadata-cache and use a fair bit of memory themselves. This is by the way they're working. Avoid them in this case. Also --cache might be not very memory efficient.
  • The CPU usage might go up quite a bit, resulting longer runs.


rmlint have been successfully used on datasets of 5 million files. See this bug report for more information: #109.