UNSQUASHFS(1)

NAME
unsquashfs - tool to uncompress, extract and list squashfs filesystems

SYNOPSIS
unsquashfs [OPTIONS] FILESYSTEM [files to extract or exclude (with -excludes) or cat (with -cat )]

DESCRIPTION
Squashfs is a highly compressed read-only filesystem for Linux. It uses either gzip/xz/lzo/lz4/zstd compression to compress both files, inodes and directories. Inodes in the system are very small and all blocks are packed to minimise data overhead. Block sizes greater than 4K are supported up to a maximum of 1Mbytes (default block size 128K).

Squashfs is intended for general read-only filesystem use, for archival use (i.e. in cases where a .tar.gz file may be used), and in constrained block device/memory systems (e.g. embedded systems) where low overhead is needed.

OPTIONS

  Filesystem extraction (filtering) options:

-d PATHNAME, -dest PATHNAME
    extract to PATHNAME, default "squashfs-root". This option also sets the prefix used when listing the filesystem.

-max LEVELS, -max-depth LEVELS
    descend at most LEVELS of directories when extracting.

-excludes
    treat files on command line as exclude files.

-ex, -exclude-list
    list of files to be excluded, terminated with ; e.g. file1 file2 ;.

-extract-file FILE
    list of directories or files to extract. One per line.

-exclude-file FILE
    list of directories or files to exclude. One per line.

-match
    abort if any extract file does not match on anything, and can not be resolved. Implies -missing-symlinks and -no-wildcards.

-follow, -follow-symlinks
    follow symlinks in extract files, and add all files/symlinks needed to resolve extract file. Implies -no-wildcards.

-missing, -missing-symlinks
    Unsquashfs will abort if any symlink can't be resolved in -follow-symlinks.

-no-wild, -no-wildcards
    do not use wildcard matching in extract and exclude names.

-r, -regex
    treat extract names as POSIX regular expressions rather than use the default shell wildcard expansion (globbing).

-all TIME, -all-time TIME
    set all file timestamps to TIME, rather than the time stored in the filesystem inode. TIME can be an unsigned 32-bit int indicating seconds since the epoch (1970-01-01) or a string value which is passed to the "date" command to parse. Any string value which the date command recognises can be used such as "now", "last week", or "Wed Feb 15 21:02:39 GMT 2023".

-cat
    cat the files on the command line to stdout.

-f, -force
    if destination directory already exists, descend into it and any sub-directories, and unlink (delete) files if they already exist before extracting to them.

-pf FILE
    output a pseudo file equivalent of the input Squashfs filesystem, use - for stdout.

  Filesystem information and listing options:

-s, -stat
    display filesystem superblock information.

-max LEVELS, -max-depth LEVELS
    descend at most LEVELS of directories when listing.

-i, -info
    print files as they are extracted.

-li, -linfo
    print files as they are extracted with file attributes (like ls -l output).

-l, -ls
    list filesystem, but do not extract files.

-ll, -lls
    list filesystem with file attributes (like ls -l output), but do not extract files.

-lln, -llnumeric
    same as -lls but with numeric uids and gids.

-lc list filesystem concisely, displaying only files and empty directories. Do not extract files.

-llc
    list filesystem concisely with file attributes, displaying only files and empty directories. Do not extract files.

-full, -full-precision
    use full precision when displaying times including seconds. Use with -linfo, -lls, -lln and -llc.

-UTC
    use UTC rather than local time zone when displaying time.

-mkfs-time
    display filesystem superblock time, which is an unsigned 32-bit int representing the time in seconds since the epoch (1970-01-01).

  Filesystem extended attribute (xattrs) options:

-no, -no-xattrs
    do not extract xattrs in file system.

-x, -xattrs
    extract xattrs in file system (default).

-xattrs-exclude REGEX
    exclude any xattr names matching REGEX. REGEX is a POSIX regular expression, e.g. -xattrs-exclude '^user.' excludes xattrs from the user namespace.

-xattrs-include REGEX
    include any xattr names matching REGEX. REGEX is a POSIX regular expression, e.g. -xattrs-include '^user.' includes xattrs from the user namespace.

  Unsquashfs runtime options:

-v, -version
    print version, licence and copyright information.

-p NUMBER, -processors NUMBER
    use NUMBER processors. By default will use the number of processors available.

-mem SIZE
    use SIZE physical memory for caches. Use K, M or G to specify Kbytes, Mbytes or Gbytes respectively. Default 512 Mbytes.

-mem-percent PERCENT
    use PERCENT physical memory for caches.

-q, -quiet
    no verbose output.

-n, -no-progress
    do not display the progress bar.

-percentage
    display a percentage rather than the full progress bar. Can be used with dialog --gauge etc.

-ig, -ignore-errors
    treat errors writing files to output as non-fatal.

-st, -strict-errors
    treat all errors as fatal.

-no-exit, -no-exit-code
    do not set exit code (to nonzero) on non-fatal errors.

  Help options:

-h, -help
    print help summary information to pager (or stdout if not a terminal).

-help-option REGEX
    print the help information for options matching REGEX to pager (or stdout if not a terminal).

-help-section SECTION
    print the help information for section SECTION to pager (or stdout if not a terminal). If SECTION does not exactly match a section name, it is treated as a regular expression, and all section names that match are displayed. Use "list" as section name to get a list of sections and their names.

-help-all
    print help information for all Unsquashfs options and sections to pager (or stdout if not a terminal).

-ho REGEX
    shorthand alternative to -help-option.

-hs SECTION
    shorthand alternative to -help-section.

-ha shorthand alternative to -help-all.

-no-pager
    do not use a pager to output help information.

-cols WIDTH
    use WIDTH columns to output help information. Useful if output is not to a terminal.

  Miscellaneous options:

-o BYTES, -offset BYTES
    skip BYTES at start of FILESYSTEM. Optionally a suffix of K, M or G can be given to specify Kbytes, Mbytes or Gbytes respectively (default 0 bytes).

-fstime
    synonym for -mkfs-time.

-e, -ef EXTRACT FILE
    synonym for -extract-file.

-exc, -excf EXCLUDE FILE
    synonym for -exclude-file.

-L  synonym for -follow-symlinks.

-pseudo-file FILE
    alternative name for -pf.

EXIT STATUS

0   The filesystem listed or extracted OK.

1   FATAL errors occurred, e.g. filesystem corruption, I/O errors. Unsquashfs did not continue and aborted.

2   Non-fatal errors occurred, e.g. no support for XATTRs, Symbolic links in output filesystem or couldn't write permissions to output filesystem. Unsquashfs continued and did not abort.

See -ignore-errors, -strict-errors and -no-exit-code options for how they affect the exit status.

DECOMPRESSORS AVAILABLE
gzip, lzo, lz4, xz, zstd, lzma

ENVIRONMENT

SQFS_CMDLINE
    If set, this is used as the directory to write the file sqfs_cmdline which contains the command line arguments given to Unsquashfs. Each command line argument is wrapped in quotes to ensure there is no ambiguity when arguments contain spaces. If the file already exists then the command line is appended to the file.

PAGER
    If set, this is used as the name of the program used to display the help text. The value can be a simple command or a pathname. The default is /usr/bin/pager.

EXAMPLES

unsquashfs IMAGE.SQFS
    Extract IMAGE.SQFS to "squashfs-root" in the current working directory.

unsquashfs -d output IMAGE.SQFS
    Extract IMAGE.SQFS to "output" in the current working directory.

unsquashfs -d . IMAGE.SQFS
    Extract IMAGE.SQFS to current working directory.

unsquashfs -linfo IMAGE.SQFS
    Output a listing of IMAGE.SQFS with file attributes to stdout, while extracting the filesystem to "squashfs-root".

unsquashfs -lls IMAGE.SQFS
    Output a listing of IMAGE.SQFS with file attributes to stdout, but do not extract the filesystem. The listing will be prefixed with "squashfs-root".

unsquashfs -d "" -lls IMAGE.SQFS
    Output a listing of IMAGE.SQFS with file attributes to stdout, but do not extract the filesystem. The listing will not be prefixed with "squashfs-root".

unsquashfs IMAGE.SQFS fs/squashfs
    Extract only the "fs/squashfs" directory.

unsquashfs IMAGE.SQFS "[Tt]est/example*"
    Extract all files beginning with "example" inside top level directories called "Test" or "test".

unsquashfs -excludes IMAGE.SQFS "test/*data*.gz"
    This will extract everything except for files that match *data*.gz in the test directory. The -excludes option tells Unsquashfs to exclude the files on the command line rather than extract them.

unsquashfs -excludes IMAGE.SQFS "... *.gz"
    This will extract everything except for files that match *.gz anywhere in the image. The "..." means this is a non-anchored exclude which matches anywhere.

unsquashfs -ex "test/*data*.gz" ; IMAGE.SQFS test
    This uses both extract and exclude options, to tell Unsquashfs to only extract the "test" directory, and to exclude any files within it that match *data*.gz.

unsquashfs -ex "... *.gz" IMAGE.SQFS test
    This uses both extract and exclude options, to tell Unsquashfs to only extract the "test" directory, and to exclude files which match "*.gz" anywhere within "test" directory or sub-directories.

unsquashfs -dest output -max-depth 2 IMAGE.SQFS
    Extract only the top two levels of IMAGE.SQFS to "output" directory.

unsquashfs -max-depth 2 IMAGE.SQFS "test/*.gz"
    Only extract the gzipped files in the test directory.

unsquashfs -llc -max-depth 2 IMAGE.SQFS "test/*.gz"
    Output a listing of the gzipped files in the test directory to stdout, but do not extract them.

unsquashfs -no-xattrs IMAGE.SQFS
    Do not extract any extended attributes. Any extended attributes in the filesystem will be ignored.

unsquashfs -xattrs-include "^user." IMAGE.SQFS
    Filter the extended attributes and only extract extended attributes in the user namespace from the Squashfs filesystem.

unsquashfs -xattrs-exclude "^user." IMAGE.SQFS
    Filter the extended attributes and do not extract any extended attributes in the user namespace from the Squashfs filesystem.

Note: when passing wildcarded names to Unsquashfs, they should be quoted (as in the above examples), to ensure that they are not processed by the shell.

AUTHOR
Written by Phillip Lougher <phillip@squashfs.org.uk>

COPYRIGHT
Copyright © 2025 Phillip Lougher <phillip@squashfs.org.uk>

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

SEE ALSO
mksquashfs(1), sqfstar(1), sqfscat(1)

The README for the Squashfs-tools 4.7.4 release, describing the new features can be read here https://github.com/plougher/squashfs-tools/blob/master/Documentation/4.7.4/README.md

The Unsquashfs usage guide can be read here https://github.com/plougher/squashfs-tools/blob/master/Documentation/4.7.4/USAGE-UNSQUASHFS.md

The CHANGELOG for Squashfs tools can be read here https://github.com/plougher/squashfs-tools/blob/master/CHANGES.md