# rmlint¶

## find duplicate files and other space waste efficiently¶

### SYNOPSIS¶

rmlint [TARGET_DIR_OR_FILES …] [//] [TAGGED_TARGET_DIR_OR_FILES …] [-] [OPTIONS]

### DESCRIPTION¶

rmlint finds space waste and other broken things on your filesystem. It’s main focus lies on finding duplicate files and directories.

It is able to find the following types of lint:

• Duplicate files and directories (and as a by-product unique files).
• Nonstripped Binaries (Binaries with debug symbols; needs to be explicitly enabled).
• Empty files and directories (also nested empty directories).
• Files with broken user or group id.

rmlint itself WILL NOT DELETE ANY FILES. It does however produce executable output (for example a shell script) to help you delete the files if you want to. Another design principle is that it should work well together with other tools like find. Therefore we do not replicate features of other well know programs, as for example pattern matching and finding duplicate filenames. However we provide many convenience options for common use cases that are hard to build from scratch with standard tools.

In order to find the lint, rmlint is given one or more directories to traverse. If no directories or files were given, the current working directory is assumed. By default, rmlint will ignore hidden files and will not follow symlinks (see Traversal Options). rmlint will first find “other lint” and then search the remaining files for duplicates.

rmlint tries to be helpful by guessing what file of a group of duplicates is the original (i.e. the file that should not be deleted). It does this by using different sorting strategies that can be controlled via the -S option. By default it chooses the first-named path on the commandline. If two duplicates come from the same path, it will also apply different fallback sort strategies (See the documentation of the -S strategy).

This behaviour can be also overwritten if you know that a certain directory contains duplicates and another one originals. In this case you write the original directory after specifying a single // on the commandline. Everything that comes after is a preferred (or a “tagged”) directory. If there are duplicates from an unpreferred and from a preferred directory, the preferred one will always count as original. Special options can also be used to always keep files in preferred directories (-k) and to only find duplicates that are present in both given directories (-m).

We advise new users to have a short look at all options rmlint has to offer, and maybe test some examples before letting it run on productive data. WRONG ASSUMPTIONS ARE THE BIGGEST ENEMY OF YOUR DATA. There are some extended example at the end of this manual, but each option that is not self-explanatory will also try to give examples.

### OPTIONS¶

#### General Options¶

-T --types="list" (default: defaults):

Configure the types of lint rmlint will look for. The list string is a comma-separated list of lint types or lint groups (other separators like semicolon or space also work though).

One of the following groups can be specified at the beginning of the list:

• all: Enables all lint types.
• defaults: Enables all lint types, but nonstripped.
• minimal: defaults minus emptyfiles and emptydirs.
• minimaldirs: defaults minus emptyfiles, emptydirs and duplicates, but with duplicatedirs.
• none: Disable all lint types [default].

Any of the following lint types can be added individually, or deselected by prefixing with a -:

• emptydirs, ed: Find empty directories.
• emptyfiles, ef: Find empty files.
• nonstripped, ns: Find nonstripped binaries.
• duplicates, df: Find duplicate files.
• duplicatedirs, dd: Find duplicate directories.

WARNING: It is good practice to enclose the description in single or double quotes. In obscure cases argument parsing might fail in weird ways, especially when using spaces as separator.

Example:

$rmlint -T "df,dd" # Only search for duplicate files and directories$ rmlint -T "all -df -dd"  # Search for all lint except duplicate files and dirs.
-o --output=spec / -O --add-output=spec (default: -o sh:rmlint.sh -o pretty:stdout -o summary:stdout -o json:rmlint.json):

Configure the way rmlint outputs its results. A spec is in the form format:file or just format. A file might either be an arbitrary path or stdout or stderr. If file is omitted, stdout is assumed. format is the name of a formatter supported by this program. For a list of formatters and their options, refer to the Formatters section below.

If -o is specified, rmlint’s default outputs are overwritten. With --O the defaults are preserved. Either -o or -O may be specified multiple times to get multiple outputs, including multiple outputs of the same format.

Examples:

$rmlint -o json # Stream the json output to stdout$ rmlint -O csv:/tmp/rmlint.csv  # Output an extra csv fle to /tmp
-c --config=spec[=value] (default: none):

Configure a format. This option can be used to fine-tune the behaviour of the existing formatters. See the Formatters section for details on the available keys.

If the value is omitted it is set to a value meaning “enabled”.

Examples:

$rmlint -c sh:link # Smartly link duplicates instead of removing$ rmlint -c progressbar:fancy  # Use a different theme for the progressbar
-z --perms[=[rwx]] (default: no check):

Only look into file if it is readable, writable or executable by the current user. Which one of the can be given as argument as one of “rwx”.

If no argument is given, “rw” is assumed. Note that r does basically nothing user-visible since rmlint will ignore unreadable files anyways. It’s just there for the sake of completeness.

By default this check is not done.

$rmlint -z rx$(echo $PATH | tr ":" " ") # Look at all executable files in$PATH

-a --algorithm=name (default: blake2b):

Choose the algorithm to use for finding duplicate files. The algorithm can be either paranoid (byte-by-byte file comparison) or use one of several file hash algorithms to identify duplicates. The following hash families are available (in approximate descending order of cryptographic strength):

sha3, blake,

sha,

highway, md

metro, murmur, xxhash

The weaker hash functions still offer excellent distribution properties, but are potentially more vulnerable to malicious crafting of duplicate files.

The full list of hash functions (in decreasing order of checksum length) is:

512-bit: blake2b, blake2bp, sha3-512, sha512

384-bit: sha3-384,

256-bit: blake2s, blake2sp, sha3-256, sha256, highway256, metro256, metrocrc256

160-bit: sha1

128-bit: md5, murmur, metro, metrocrc

64-bit: highway64, xxhash.

The use of 64-bit hash length for detecting duplicate files is not recommended, due to the probability of a random hash collision.

-p --paranoid / -P --less-paranoid (default):

Increase or decrease the paranoia of rmlint’s duplicate algorithm. Use -p if you want byte-by-byte comparison without any hashing.

• -p is equivalent to –algorithm=paranoid
• -P is equivalent to –algorithm=highway256
• -PP is equivalent to –algorithm=metro256
• -PPP is equivalent to –algorithm=metro
-v --loud / -V --quiet:

Increase or decrease the verbosity. You can pass these options several times. This only affects rmlint’s logging on stderr, but not the outputs defined with -o. Passing either option more than three times has no further effect.

-g --progress / -G --no-progress (default):

Show a progressbar with sane defaults.

Convenience shortcut for -o progressbar -o summary -o sh:rmlint.sh -o json:rmlint.json -VVV.

NOTE: This flag clears all previous outputs. If you want additional outputs, specify them after this flag using -O.

-D --merge-directories (default: disabled):

Makes rmlint use a special mode where all found duplicates are collected and checked if whole directory trees are duplicates. Use with caution: You always should make sure that the investigated directory is not modified during rmlint’s or its removal scripts run.

IMPORTANT: Definition of equal: Two directories are considered equal by rmlint if they contain the exact same data, no matter how the files containing the data are named. Imagine that rmlint creates a long, sorted stream out of the data found in the directory and compares this in a magic way to another directory. This means that the layout of the directory is not considered to be important by default. Also empty files will not count as content. This might be surprising to some users, but remember that rmlint generally cares only about content, not about any other metadata or layout. If you want to only find trees with the same hierarchy you should use --honour-dir-layout / -j.

Output is deferred until all duplicates were found. Duplicate directories are printed first, followed by any remaining duplicate files that are isolated or inside of any original directories.

–rank-by applies for directories too, but ‘p’ or ‘P’ (path index) has no defined (i.e. useful) meaning. Sorting takes only place when the number of preferred files in the directory differs.

NOTES:

• This option enables --partial-hidden and -@ (--see-symlinks) for convenience. If this is not desired, you should change this after specifying -D.
• This feature might add some runtime for large datasets.
• When using this option, you will not be able to use the -c sh:clone option. Use -c sh:link as a good alternative.
-j --honour-dir-layout (default: disabled):

Only recognize directories as duplicates that have the same path layout. In other words: All duplicates that build the duplicate directory must have the same path from the root of each respective directory. This flag makes no sense without --merge-directories.

-y --sort-by=order (default: none):

During output, sort the found duplicate groups by criteria described by order. order is a string that may consist of one or more of the following letters:

• s: Sort by size of group.
• a: Sort alphabetically by the basename of the original.
• m: Sort by mtime of the original.
• p: Sort by path-index of the original.
• o: Sort by natural found order (might be different on each run).
• n: Sort by number of files in the group.

The letter may also be written uppercase (similar to -S / --rank-by) to reverse the sorting. Note that rmlint has to hold back all results to the end of the run before sorting and printing.

-w --with-color (default) / -W --no-with-color:

Use color escapes for pretty output or disable them. If you pipe rmlints output to a file -W is assumed automatically.

-h --help / -H --show-man:

Show a shorter reference help text (-h) or the full man page (-H).

--version:

Print the version of rmlint. Includes git revision and compile time features. Please include this when giving feedback to us.

#### Traversal Options¶

-s --size=range (default: “1”):

Only consider files as duplicates in a certain size range. The format of range is min-max, where both ends can be specified as a number with an optional multiplier. The available multipliers are:

• C (1^1), W (2^1), B (512^1), K (1000^1), KB (1024^1), M (1000^2), MB (1024^2), G (1000^3), GB (1024^3),
• T (1000^4), TB (1024^4), P (1000^5), PB (1024^5), E (1000^6), EB (1024^6)

The size format is about the same as dd(1) uses. A valid example would be: “100KB-2M”. This limits duplicates to a range from 100 Kilobyte to 2 Megabyte.

It’s also possible to specify only one size. In this case the size is interpreted as “bigger or equal”. If you want to filter for files up to this size you can add a - in front (-s -1M == -s 0-1M).

Edge case: The default excludes empty files from the duplicate search. Normally these are treated specially by rmlint by handling them as other lint. If you want to include empty files as duplicates you should lower the limit to zero:

#### Rarely used, miscellaneous options¶

The number of threads to use during file tree traversal and hashing. rmlint probably knows better than you how to set this value, so just leave it as it is. Setting it to 1 will also not make rmlint a single threaded program.

-u --limit-mem=size:

Apply a maximum number of memory to use for hashing and –paranoid. The total number of memory might still exceed this limit though, especially when setting it very low. In general rmlint will however consume about this amount of memory plus a more or less constant extra amount that depends on the data you are scanning.

The size-description has the same format as for –size, therefore you can do something like this (use this if you have 1GB of memory available):

$rmlint -u 512M # Limit paranoid mem usage to 512 MB -q --clamp-low=[fac.tor|percent%|offset] (default: 0) / -Q --clamp-top=[fac.tor|percent%|offset] (default: 1.0): The argument can be either passed as factor (a number with a . in it), a percent value (suffixed by %) or as absolute number or size spec, like in --size. Only look at the content of files in the range of from low to (including) high. This means, if the range is less than -q 0% to -Q 100%, than only partial duplicates are searched. If the file size is less than the clamp limits, the file is ignored during traversing. Be careful when using this function, you can easily get dangerous results for small files. This is useful in a few cases where a file consists of a constant sized header or footer. With this option you can just compare the data in between. Also it might be useful for approximate comparison where it suffices when the file is the same in the middle part. Example:$ rmlint -q 10% -Q 512M  # Only read the last 90% of a file, but read at max. 512MB

-Z --mtime-window=T (default: -1):

Only consider those files as duplicates that have the same content and the same modification time (mtime) within a certain window of T seconds. If T is 0, both files need to have the same mtime. For T=1 they may differ one second and so on. If the window size is negative, the mtime of duplicates will not be considered. T may be a floating point number.

However, with three (or more) files, the mtime difference between two duplicates can be bigger than the mtime window T, i.e. several files may be chained together by the window. Example: If T is 1, the four files fooA (mtime: 00:00:00), fooB (00:00:01), fooC (00:00:02), fooD (00:00:03) would all belong to the same duplicate group, although the mtime of fooA and fooD differs by 3 seconds.

--with-fiemap (default) / --without-fiemap:

Enable or disable reading the file extents on rotational disk in order to optimize disk access patterns. If this feature is not available, it is disabled automatically.

### FORMATTERS¶

• csv: Output all found lint as comma-separated-value list.

Available options:

• no_header: Do not write a first line describing the column headers.
• sh: Output all found lint as shell script This formatter is activated

as default.

Available options:

• cmd: Specify a user defined command to run on duplicates. The command can be any valid /bin/sh-expression. The duplicate path and original path can be accessed via "$1" and "$2". The command will be written to the user_command function in the sh-file produced by rmlint.

• handler Define a comma separated list of handlers to try on duplicate files in that given order until one handler succeeds. Handlers are just the name of a way of getting rid of the file and can be any of the following:

• clone: For reflink-capable filesystems only. Try to clone both files with the FIDEDUPERANGE ioctl(3p) (or BTRFS_IOC_FILE_EXTENT_SAME on older kernels). This will free up duplicate extents. Needs at least kernel 4.2. Use this option when you only have read-only access to a btrfs filesystem but still want to deduplicate it. This is usually the case for snapshots.
• hardlink: Replace the duplicate file with a hardlink to the original file. The resulting files will have the same inode number. Fails if both files are not on the same partition. You can use ls -i to show the inode number of a file and find -samefile <path> to find all hardlinks for a certain file.
• symlink: Tries to replace the duplicate file with a symbolic link to the original. This handler never fails.
• remove: Remove the file using rm -rf. (-r for duplicate dirs). This handler never fails.
• usercmd: Use the provided user defined command (-c sh:cmd=something). This handler never fails.

Default is remove.

• hardlink: Shortcut for -c sh:handler=hardlink,symlink. Use this if you want to hardlink files, but want to fallback for duplicates that lie on different devices.

• json: Print a JSON-formatted dump of all found reports. Outputs all lint as a json document. The document is a list of dictionaries, where the first and last element is the header and the footer. Everything between are data-dictionaries.

Available options:

• no_footer=[true|false]: Print the footer with statistics (default: true)
• oneline=[true|false]: Print one json document per line (default: false) This is useful if you plan to parse the output line-by-line, e.g. while rmlint is sill running.

This formatter is extremely useful if you’re in need of scripting more complex behaviour, that is not directly possible with rmlint’s built-in options. A very handy tool here is jq. Here is an example to output all original files directly from a rmlint run:

$rmlint -o | json jq -r '.[1:-1][] | select(.is_original) | .path' • py: Outputs a python script and a JSON document, just like the json formatter. The JSON document is written to .rmlint.json, executing the script will make it read from there. This formatter is mostly intended for complex use-cases where the lint needs special handling that you define in the python script. Therefore the python script can be modified to do things standard rmlint is not able to do easily. • uniques: Outputs all unique paths found during the run, one path per line. This is often useful for scripting purposes. • stamp: Outputs a timestamp of the time rmlint was run. See also the --newer-than and --newer-than-stamp file option. Available options: • iso8601=[true|false]: Write an ISO8601 formatted timestamps or seconds since epoch? • progressbar: Shows a progressbar. This is meant for use with stdout or stderr [default]. See also: -g (--progress) for a convenience shortcut option. Available options: • update_interval=number: Number of milliseconds to wait between updates. Higher values use less resources (default 50). • ascii: Do not attempt to use unicode characters, which might not be supported by some terminals. • fancy: Use a more fancy style for the progressbar. • pretty: Shows all found items in realtime nicely colored. This formatter is activated as default. • summary: Shows counts of files and their respective size after the run. Also list all written output files. • fdupes: Prints an output similar to the popular duplicate finder fdupes(1). At first a progressbar is printed on stderr. Afterwards the found files are printed on stdout; each set of duplicates gets printed as a block separated by newlines. Originals are highlighted in green. At the bottom a summary is printed on stderr. This is mostly useful for scripts that were set up for parsing fdupes output. We recommend the json formatter for every other scripting purpose. Available options: • omitfirst: Same as the -f / --omitfirst option in fdupes(1). Omits the first line of each set of duplicates (i.e. the original file. • sameline: Same as the -1 / --sameline option in fdupes(1). Does not print newlines between files, only a space. Newlines are printed only between sets of duplicates. ### OTHER STAND-ALONE COMMANDS¶ rmlint --gui: rmlint --hash [paths...]: Start the optional graphical frontend to rmlint called Shredder. This will only work when Shredder and its dependencies were installed. See also: http://rmlint.readthedocs.org/en/latest/gui.html The gui has its own set of options, see --gui --help for a list. These should be placed at the end, ie rmlint --gui [options] when calling it from commandline. Make rmlint work as a multi-threaded file hash utility, similar to the popular md5sum or sha1sum utilities, but faster and with more algorithms. A set of paths given on the commandline or from stdin is hashed using one of the available hash algorithms. Use rmlint --hash -h to see options. Check if the paths given on the commandline all have equal content. If all paths are equal and no other error happened, rmlint will exit with an exit code 0. Otherwise it will exit with a nonzero exit code. All other options can be used as normal, but note that no other formatters (sh, csv etc.) will be executed by default. At least two paths need to be passed. Note: This even works for directories and also in combination with paranoid mode (pass -pp for byte comparison); remember that rmlint does not care about the layout of the directory, but only about the content of the files in it. At least two paths need to be given to the commandline. By default this will use hashing to compare the files and/or directories. If the filesystem supports files sharing physical storage between multiple files, and if src and dest have same content, this command makes the data in the src file appear the dest file by sharing the underlying storage. This command is similar to cp --reflink=always except that it (a) checks that src and dest have identical data, and it makes no changes to dest’s metadata. Running with -r option will enable deduplication of read-only [btrfs] snapshots (requires root). Tests whether file1 and file2 are reflinks (reference same data). Return codes: 0: files are reflinks 1: files are not reflinks 3: not a regular file 4: file sizes differ 5: fiemaps can’t be read 6: file1 and file2 are the same path 7: file1 and file2 are the same file under different mountpoints 8: files are hardlinks 9: files are symlinks (TODO) 10: files are not on same device 11: other error encountered ### EXAMPLES¶ This is a collection of common use cases and other tricks: • Check the current working directory for duplicates.$ rmlint

• Show a progressbar:

$rmlint -g • Quick re-run on large datasets using different ranking criteria on second run:$ rmlint large_dir/ # First run; writes rmlint.json

$rmlint --replay rmlint.json large_dir -S MaD • Merge together previous runs, but prefer the originals to be from b.json and make sure that no files are deleted from b.json:$ rmlint --replay a.json // b.json -k

• Search only for duplicates and duplicate directories

$rmlint -T "df,dd" . • Compare files byte-by-byte in current directory:$ rmlint -pp .

• Find duplicates with same basename (excluding extension):

$rmlint -e • Do more complex traversal using find(1).$ find /usr/lib -iname '*.so' -type f | rmlint - # find all duplicate .so files

$find /usr/lib -iname '*.so' -type f -print0 | rmlint -0 # as above but handles filenames with newline character in them$ find ~/pics -iname '*.png' | ./rmlint - # compare png files only

• Limit file size range to investigate:

$rmlint -s 2GB # Find everything >= 2GB$ rmlint -s 0-2GB  # Find everything <  2GB

• Only find writable and executable files:

$rmlint --perms wx • Reflink if possible, else hardlink duplicates to original if possible, else replace duplicate with a symbolic link:$ rmlint -c sh:link

• Inject user-defined command into shell script output:

$rmlint -o sh -c sh:cmd='echo "original:" "$2" "is the same as" "$1"' • Use shred to overwrite the contents of a file fully:$ rmlint -c 'sh:cmd=shred -un 10 "$1"' • Use data as master directory. Find only duplicates in backup that are also in data. Do not delete any files in data:$ rmlint backup // data --keep-all-tagged --must-match-tagged

• Compare if the directories a b c and are equal

$rmlint --equal a b c && echo "Files are equal" || echo "Files are not equal" • Test if two files are reflinks$ rmlint --is-reflink a b && echo "Files are reflinks" || echo "Files are not reflinks".

• Cache calculated checksums for next run. The checksums will be written to the extended file attributes:

$rmlint --xattr • Produce a list of unique files in a folder:$ rmlint -o uniques

• Produce a list of files that are unique, including original files (“one of each”):

$rmlint t -o json -o uniques:unique_files | jq -r '.[1:-1][] | select(.is_original) | .path' | sort > original_files$ cat unique_files original_files

### PROBLEMS¶

1. False Positives: Depending on the options you use, there is a very slight risk of false positives (files that are erroneously detected as duplicate). The default hash function (blake2b) is very safe but in theory it is possible for two files to have then same hash. If you had 10^73 different files, all the same size, then the chance of a false positive is still less than 1 in a billion. If you’re concerned just use the --paranoid (-pp) option. This will compare all the files byte-by-byte and is not much slower than blake2b (it may even be faster), although it is a lot more memory-hungry.
2. File modification during or after rmlint run: It is possible that a file that rmlint recognized as duplicate is modified afterwards, resulting in a different file. If you use the rmlint-generated shell script to delete the duplicates, you can run it with the -p option to do a full re-check of the duplicate against the original before it deletes the file. When using -c sh:hardlink or -c sh:symlink care should be taken that a modification of one file will now result in a modification of all files. This is not the case for -c sh:reflink or -c sh:clone. Use -c sh:link to minimise this risk.

Reading the manpages o these tools might help working with rmlint:

• find(1)
• rm(1)
• cp(1)

Extended documentation and an in-depth tutorial can be found at:

### BUGS¶

If you found a bug, have a feature requests or want to say something nice, please visit https://github.com/sahib/rmlint/issues.

Please make sure to describe your problem in detail. Always include the version of rmlint (--version). If you experienced a crash, please include at least one of the following information with a debug build of rmlint:

• gdb --ex run -ex bt --args rmlint -vvv [your_options]
• valgrind --leak-check=no rmlint -vvv [your_options]

You can build a debug build of rmlint like this:

• git clone git@github.com:sahib/rmlint.git
• cd rmlint
• scons GDB=1 DEBUG=1
• sudo scons install  # Optional