MKSQUASHFS(1) User Commands MKSQUASHFS(1)

mksquashfs - tool to create and append to squashfs filesystems

mksquashfs source1 source2 ... FILESYSTEM [OPTIONS] [-e list of exclude dirs/files]

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.

set data block to BLOCK_SIZE. Default 128 Kbytes. Optionally a suffix of K or M can be given to specify Kbytes or Mbytes respectively.
select COMP compression. Compressors available: gzip (default), lzo, lz4, xz, zstd, lzma.
do not compress inode table.
do not compress the uid/gid table (implied by -noI).
do not compress data blocks.
do not compress fragment blocks.
do not compress extended attributes.
do not compress any of the data or metadata. This is equivalent to specifying -noI -noD -noF and -noX.

read uncompressed tar file from standard in (stdin).
act like tar, and do not strip leading directories from source files.
alternative name for -no-strip.
act like cpio, and read file pathnames from standard in (stdin).
like -cpiostyle, but filenames are null terminated. Can be used with find -print0 action.
build filesystems that are reproducible (default).
build filesystems that are not reproducible.
set filesystem creation timestamp to TIME. 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".
set all file timestamps to TIME. 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".
set root directory time to TIME. 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".
set root directory permissions to octal MODE.
set root directory owner to specified VALUE, VALUE can be either an integer uid or user name.
set root directory group to specified VALUE, VALUE can be either an integer gid or group name.
make all files owned by root.
set all file uids to specified VALUE, VALUE can be either an integer uid or user name.
set all file gids to specified VALUE, VALUE can be either an integer gid or group name.
make pseudo file uids and gids override -all-root, -force-uid and -force-gid options.
do not make filesystem exportable via NFS (-tar default).
make filesystem exportable via NFS (default).
do not detect sparse files.
do not pack tail ends into fragments (default).
pack tail ends into fragments.
do not use fragments.
do not perform duplicate checking.
do not hardlink files, instead store duplicates.
if one source directory is specified, create a root directory containing that directory, rather than the contents of the directory.

add pseudo file definition. The definition should be quoted.
add list of pseudo file definitions from PSEUDO-FILE, use - for stdin. Pseudo file definitions should not be quoted.
sort files according to priorities in SORT_FILE. One file or dir with priority per line. Priority -32768 to 32767, default priority 0.
list of exclude dirs/files. One per line.
allow extended shell wildcards (globbing) to be used in exclude dirs/files.
allow POSIX regular expressions to be used in exclude dirs/files.
descend at most LEVELS of directories when scanning filesystem.
do not cross filesystem boundaries. If a directory crosses the boundary, create an empty directory for each mount point. If a file crosses the boundary ignore it.
do not cross filesystem boundaries. Like -one-file-system option except directories are also ignored if they cross the boundary.

do not store extended attributes.
store extended attributes (default).
exclude any xattr names matching REGEX. REGEX is a POSIX regular expression, e.g. -xattrs-exclude '^user.' excludes xattrs from the user namespace.
include any xattr names matching REGEX. REGEX is a POSIX regular expression, e.g. -xattrs-include '^user.' includes xattrs from the user namespace.
add the xattr NAME with VAL to files. If an user xattr it will be added to regular files and directories (see man 7 xattr). Otherwise it will be added to all files. VAL by default will be treated as binary (i.e. an uninterpreted byte sequence), but it can be prefixed with 0s, where it will be treated as base64 encoded, or prefixed with 0x, where val will be treated as hexidecimal. Additionally it can be prefixed with 0t where this encoding is similar to binary encoding, except backslashes are specially treated, and a backslash followed by 3 octal digits can be used to encode any ASCII character, which obviously can be used to encode control codes. The option can be repeated multiple times to add multiple xattrs.

print version, licence and copyright message.
treat normally ignored errors as fatal.
no verbose output.
print files written to filesystem.
do not display the progress bar.
display progress bar when using the -info option.
display a percentage rather than the full progress bar. Can be used with dialog --gauge etc.
throttle the I/O input rate by the given percentage. This can be used to reduce the I/O and CPU consumption of Mksquashfs.
limit the I/O input rate to the given percentage. This can be used to reduce the I/O and CPU consumption of Mksquashfs (alternative to -throttle).
use NUMBER processors. By default will use number of processors available.
use SIZE physical memory for caches. Use K, M or G to specify Kbytes, Mbytes or Gbytes respectively.
use PERCENT physical memory for caches. Default 25%.
print default memory usage in Mbytes.

do not append to existing filesystem.
when appending source files/directories, make the original root become a subdirectory in the new root called NAME, rather than adding the new source items to the original root.
do not generate a recovery file.
use NAME as the directory to store the recovery file.
recover filesystem data using recovery file NAME.

evaluate EXPRESSION on every file, and execute ACTION if it returns TRUE.
as above, but log expression evaluation results and actions performed.
as above, but only log expressions which return TRUE.
as above, but only log expressions which return FALSE.
as action, but read actions from FILE.
as -log-action, but read actions from FILE.
as -true-action, but read actions from FILE.
as -false-action, but read actions from FILE.

tar files often do not store permissions for intermediate directories. This option sets the default directory permissions to octal MODE, rather than 0755. This also sets the root inode mode.
tar files often do not store uids for intermediate directories. This option sets the default directory owner to UID, rather than the user running Mksquashfs. This also sets the root inode uid.
tar files often do not store gids for intermediate directories. This option sets the default directory group to GID, rather than the group of the user running Mksquashfs. This also sets the root inode gid.
allow tar files to be concatenated together and fed to Mksquashfs. Normally a tarfile has two consecutive 512 byte blocks filled with zeros which means EOF and Mksquashfs will stop reading after the first tar file on encountering them. This option makes Mksquashfs ignore the zero filled blocks.

do not pad filesystem to a multiple of 4K.
skip OFFSET bytes at the beginning of FILESYSTEM. Optionally a suffix of K, M or G can be given to specify Kbytes, Mbytes or Gbytes respectively. Default 0 bytes.
synonym for -offset.

alternative name for -mkfs-time.
alternative name for -tailends.
alternative name for -all-root.
alternative name for -noI.
alternative name for -noId.
alternative name for -noD.
alternative name for -noF.
alternative name for -noX.
output this options text to stdout.
output this options text to stdout.
print compressor options for selected compressor.

create a directory.
modify filename.
create a block device.
create a character device.
create file from stdout of command.
create a symbolic link.
create a socket (s) or FIFO (f).
create an extended attribute.
create a hard-link to linkname.
same, but link to pseudo file.
create a directory with timestamp time.
modify a file with timestamp time.
create block device with timestamp time.
create char device with timestamp time.
create file with timestamp time.
create symlink with timestamp time.
create socket/fifo with timestamp time.

COMPRESSION-LEVEL should be 1 .. 9 (default 9).
WINDOW-SIZE should be 8 .. 15 (default 15).
Compress using strategy1,strategy2,...,strategyN in turn and choose the best compression. Available strategies: default, filtered, huffman_only, run_length_encoded and fixed.

Where ALGORITHM is one of: lzo1x_1, lzo1x_1_11, lzo1x_1_12, lzo1x_1_15, lzo1x_999 (default).
COMPRESSION-LEVEL should be 1 .. 9 (default 8) Only applies to lzo1x_999 algorithm.

Compress using LZ4 High Compression.

Compress using filter1,filter2,...,filterN in turn (in addition to no filter), and choose the best compression. Available filters: x86, arm, armthumb, powerpc, sparc, ia64.
Use DICT-SIZE as the XZ dictionary size. The dictionary size can be specified as a percentage of the block size, or as an absolute value. The dictionary size must be less than or equal to the block size and 8192 bytes or larger. It must also be storable in the xz header as either 2^n or as 2^n+2^(n+1). Example dict-sizes are 75%, 50%, 37.5%, 25%, or 32K, 16K, 8K etc.

COMPRESSION-LEVEL should be 1 .. 22 (default 15).

(no options) (deprecated - no kernel support)

If set, this is used as the filesystem creation timestamp. Also any file timestamps which are after SOURCE_DATE_EPOCH will be clamped to SOURCE_DATE_EPOCH. See https://reproducible-builds.org/docs/source-date-epoch/ for more information.

Create a Squashfs filesystem from the contents of DIRECTORY, writing the output to IMAGE.SQSH. Mksquashfs will use the default compressor (normally gzip), and block size of 128 Kbytes.
Create a Squashfs filesystem containing DIRECTORY and FILE1 and FILE2. If multiple sources are specified on the command line they will be combined into a single directory.
Use a block size of 1 Mbyte and Zstandard compression to create the filesystem.
Exclude file1 and file2 from DIRECTORY when creating filesystem. No wildcard matching of files.
Exclude anything in DIRECTORY which matches the wildcard pattern "*.gz".
Exclude files which match the wildcard pattern "*.gz" anywhere within DIRECTORY and its sub-directories. The initial "..." indicates the wildcard pattern is "non-anchored" and will match anywhere.

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

Create a directory called "build_dir" in the output filesystem.
Create a reference called "version.txt" to a file outside DIRECTORY, which acts as if the file "/tmp/build/version" was copied or hard-linked into DIRECTORY before calling Mksquashfs.
Create a file called "date.txt" which holds the output (stdout) from running the "date" command.
As above, but, showing that filenames can have spaces, if they are quoted. The quotes need to be blackslashed to protect them from the shell.
Create a file containing the contents of partition /dev/sda1". Ordinarily Mksquashfs given a device, fifo, or named socket will place that special file within the Squashfs filesystem, the above allows input from these special files to be captured and placed in the Squashfs filesystem. Note there are no other sources than the pseudo file, and so the command line source is "-". If there are no other sources than pseudo files, the root (/) directory must be defined too, as seen in this example.
Transcode IMAGE.SQFS to NEW.SQFS by piping the pseudo file output from Unsquashfs to Mksquashfs using stdout and stdin. This can convert from earlier Squashfs filesystems or change compression algorithm, block size etc. without needing to unpack into an intermediate directory or file.

Note: pseudo file definitions should be quoted (as in the above examples), to ensure that they are passed to Mksquashfs as a single argument, and to ensure that they are not processed by the shell.

Do not store any extended attributes in the Squashfs filesystem. Any extended attributes in the source files will be ignored.
Filter the extended attributes in the source files, and only store extended attributes in the user namespace in the Squashfs filesystem.
Filter the extended attributes in the source files, and don't store any extended attributes in the user namespace in the Squashfs filesystem.
Add the extended attribute called "user.comment" with the content "hello world" to all files and directories in the Squashfs filesystem.
Add the extended attribute called "user.comment" to all files and directories, but in this case the contents of the extended attribute will be "hello world" with a trailing newline character (012 octal).
Add the extended attribute called "user.comment" to all files and directories, where the value is given in base64 encoding, representing "hello world".
Filter the extended attributes but only in regular files (type f), and only store extended attributes in the user namespace.
Add the extended attribute called "user.comment" to the file called "hello_world", with the contents of the extended attribute being "salve mundi" with a trailing newline character (012 octal).

Specify that any files matching the wildcards "*.jpg" and "*.mpg" should not be compressed. Additionally, it also specifies any files matching the wildcard "*.img" and are larger than 1 Gigabyte should be uncompressed too. This shows test operators can be combined with logical expressions.
If any files within DIRECTORY are not readable by "others", then make them readable by others in the Squashfs filesystem.
As previous, match on any files which are not readable by "others", but, in this case change the owner of the file to "phillip" in the Squashfs filesystem.
Delete any symbolic link within DIRECTORY which points outside of DIRECTORY, i.e. will be unresolvable in the Squashfs filesystem.
Create a Squashfs filesystem containing the two top most levels (contents of DIRECTORY and immediate sub-directories), and exclude anything at level 3 or below.
Filter the extended attributes but only in regular files (type f), and only store extended attributes in the user namespace.

Note: actions should be quoted (as in the above examples), to ensure that they are passed to Mksquashfs as a single argument, and to ensure that they are not processed by the shell.

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

Copyright © 2023 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.

unsquashfs(1), sqfstar(1), sqfscat(1)

The README for the Squashfs-tools 4.6.1 release, describing the new features can be read here https://github.com/plougher/squashfs-tools/blob/master/README-4.6.1

The Squashfs-tools USAGE guide can be read here https://github.com/plougher/squashfs-tools/blob/master/USAGE-4.6

The ACTIONS-README file describing how to use the new actions feature can be read here https://github.com/plougher/squashfs-tools/blob/master/ACTIONS-README

April 2024 mksquashfs version 4.6.1