Added KB page about duperemove

knowledge base/duperemove.md

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+# Duperemove
+
+Finds duplicated extents and submits them for deduplication.
+
+When given a list of files, `duperemove` hashes their contents block by block and compares them.
+
+When given the `-d` option, `duperemove` also submits duplicated extents for deduplication using the Linux kernel extent-same ioctl.
+
+`duperemove` can store the hashes it computes in a hashfile. If given an existing hashfile in input, it only computes hashes for those files which have changed since the last run. This lets you run `duperemove` repeatedly on your data as it changes, without having to re-checksum unchanged data.
+
+`duperemove` can also take input from `fdupes`, given the `--fdupes` option.
+
+## TL;DR
+
+```shell
+# Recursively search for duplicated extents in a directory.
+duperemove -hr path/to/directory
+
+# Recursively deduplicate duplicated extents on a Btrfs or XFS filesystem.
+# XFS deduplication is still experimental at the time of writing.
+duperemove -Adhr path/to/directory
+
+# Store extent hashes in a file.
+# Hogs less memory and can be reused on subsequent runs.
+duperemove -Adhr --hashfile=path/to/hashfile path/to/directory
+
+# List the files tracked by hashfiles.
+duperemove -L --hashfile=path/to/hashfile
+
+# Limit threads.
+# I/O threads are used for hashing and in the deduplication stage.
+# CPU threads are used in the duplicate extent finding stage.
+duperemove -Adhr --hashfile=path/to/hashfile --io-threads=N --cpu-threads=N path/to/directory
+```
+
+## Sources
+
+- [Website]
+- [cheat.sh]
+- [manpage]
+
+[cheat.sh]: https://cheat.sh/duperemove
+[manpage]: https://markfasheh.github.io/duperemove/duperemove.html
+[website]: https://markfasheh.github.io/duperemove/