Provided by: squashfs-tools_4.5.1-1_amd64 
NAME
mksquashfs - tool to create and append to squashfs filesystems
SYNOPSIS
mksquashfs source1 source2 ... FILESYSTEM [OPTIONS] [-e list of exclude dirs/files]
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 build options:
-tar read uncompressed tar file from standard in (stdin).
-no-strip
act like tar, and do not strip leading directories from source files.
-tarstyle
alternative name for -no-strip.
-cpiostyle
act like cpio, and read files from standard in (stdin).
-cpiostyle0
like -cpiostyle, but filenames are null terminated.
-comp COMP
select COMP compression. Compressors available: gzip (default), lzo, lz4, xz, zstd,
lzma.
-b BLOCK_SIZE
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.
-reproducible
build filesystems that are reproducible (default).
-not-reproducible
build filesystems that are not reproducible.
-mkfs-time TIME
set filesystem creation timestamp to TIME, which is an unsigned 32-bit int
indicating seconds since the epoch (1970-01-01).
-fstime TIME
synonym for mkfs-time.
-all-time TIME
set all file timestamps to TIME, which is an unsigned 32-bit int indicating seconds
since the epoch (1970-01-01).
-no-exports
don't make filesystem exportable via NFS (-tar default).
-exports
make filesystem exportable via NFS (default).
-no-sparse
don't detect sparse files.
-no-xattrs
don't store extended attributes.
-xattrs
store extended attributes (default).
-noI do not compress inode table.
-noId do not compress the uid/gid table (implied by -noI).
-noD do not compress data blocks.
-noF do not compress fragment blocks.
-noX do not compress extended attributes.
-no-tailends
don't pack tail ends into fragments (default).
-tailends
pack tail ends into fragments.
-no-fragments
do not use fragments.
-always-use-fragments
use fragment blocks for files larger than block size.
-no-duplicates
do not perform duplicate checking.
-no-hardlinks
do not hardlink files, instead store duplicates.
-all-root
make all files owned by root.
-root-time TIME
set root directory time to TIME.
-root-mode MODE
set root directory permissions to octal MODE.
-root-uid UID
set root directory owner to UID.
-root-gid GID
set root directory group to GID.
-force-uid UID
set all file uids to UID.
-force-gid GID
set all file gids to GID.
-keep-as-directory
if one source directory is specified, create a root directory containing that
directory, rather than the contents of the directory.
-action ACTION@EXPRESSION
evaluate EXPRESSION on every file, and execute ACTION if it returns TRUE.
-log-action ACTION@EXPRESSION
as above, but log expression evaluation results and actions performed.
-true-action ACTION@EXPRESSION
as above, but only log expressions which return TRUE.
-false-action ACTION@EXPRESSION
as above, but only log expressions which return FALSE.
-action-file FILE
as action, but read actions from FILE.
-log-action-file FILE
as -log-action, but read actions from FILE.
-true-action-file FILE
as -true-action, but read actions from FILE.
-false-action-file FILE
as -false-action, but read actions from FILE.
Filesystem filter options:
-p PSEUDO-DEFINITION
Add pseudo file definition. The definition should be quoted.
-pf PSEUDO-FILE
Add list of pseudo file definitions. Pseudo file definitions in pseudo-files
should not be quoted.
-sort SORT_FILE
sort files according to priorities in SORT_FILE. One file or dir with priority per
line. Priority -32768 to 32767, default priority 0.
-ef EXCLUDE_FILE
list of exclude dirs/files. One per line.
-wildcards
Allow extended shell wildcards (globbing) to be used in exclude dirs/files.
-regex Allow POSIX regular expressions to be used in exclude dirs/files.
-one-file-system
Do not cross filesystem boundaries when scanning sources.
Filesystem append options:
-noappend
do not append to existing filesystem.
-root-becomes NAME
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.
Mksquashfs runtime options:
-version
print version, licence and copyright message.
-exit-on-error
treat normally ignored errors as fatal.
-recover NAME
recover filesystem data using recovery file NAME.
-no-recovery
don't generate a recovery file.
-recovery-path NAME
use NAME as the directory to store the recovery file.
-quiet no verbose output.
-info print files written to filesystem.
-no-progress
don't display the progress bar.
-progress
display progress bar when using the -info option.
-throttle PERCENTAGE
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 PERCENTAGE
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).
-processors NUMBER
Use NUMBER processors. By default will use number of processors available.
-mem SIZE
Use SIZE physical memory. Optionally a suffix of K, M or G can be given to specify
Kbytes, Mbytes or Gbytes respectively.
Expert options (these may make the filesystem unmountable):
-nopad do not pad filesystem to a multiple of 4K.
-offset OFFSET
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.
-o OFFSET
synonym for -offset.
Miscellaneous options:
-root-owned
alternative name for -all-root.
-noInodeCompression
alternative name for -noI.
-noIdTableCompression
alternative name for -noId.
-noDataCompression
alternative name for -noD.
-noFragmentCompression
alternative name for -noF.
-noXattrCompression
alternative name for -noX.
-help output this options text to stdout.
-h output this options text to stdout.
-Xhelp print compressor options for selected compressor.
PSEUDO FILE DEFINITION FORMAT
-p "filename d mode uid gid"
create a directory.
-p "filename m mode uid gid"
modify filename.
-p "filename b mode uid gid major minor"
create a block device.
-p "filename c mode uid gid major minor"
create a character device.
-p "filename f mode uid gid command"
create file from stdout of command.
-p "filename s mode uid gid symlink"
create a symbolic link.
-p "filename i mode uid gid [s|f]"
create a socket (s) or FIFO (f).
-p "filename l linkname"
create a hard-link to linkname.
-p "filename L pseudo_filename"
same, but link to pseudo file.
-p "filename D time mode uid gid"
create a directory with timestamp time.
-p "filename M time mode uid gid"
modify a file with timestamp time.
-p "filename B time mode uid gid major minor"
create block device with timestamp time.
-p "filename C time mode uid gid major minor"
create char device with timestamp time.
-p "filename F time mode uid gid command"
create file with timestamp time.
-p "filename S time mode uid gid symlink"
create symlink with timestamp time.
-p "filename I time mode uid gid [s|f]"
create socket/fifo with timestamp time.
COMPRESSORS AVAILABLE AND COMPRESSOR SPECIFIC OPTIONS
gzip (default):
-Xcompression-level COMPRESSION-LEVEL
COMPRESSION-LEVEL should be 1 .. 9 (default 9).
-Xwindow-size WINDOW-SIZE
WINDOW-SIZE should be 8 .. 15 (default 15).
-Xstrategy strategy1,strategy2,...,strategyN
Compress using strategy1,strategy2,...,strategyN in turn and choose the best
compression. Available strategies: default, filtered, huffman_only,
run_length_encoded and fixed.
lzo:
-Xalgorithm ALGORITHM
Where ALGORITHM is one of: lzo1x_1, lzo1x_1_11, lzo1x_1_12, lzo1x_1_15, lzo1x_999
(default).
-Xcompression-level COMPRESSION-LEVEL
COMPRESSION-LEVEL should be 1 .. 9 (default 8) Only applies to lzo1x_999 algorithm.
lz4:
-Xhc Compress using LZ4 High Compression.
xz:
-Xbcj filter1,filter2,...,filterN
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.
-Xdict-size DICT-SIZE
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.
zstd:
-Xcompression-level COMPRESSION-LEVEL
COMPRESSION-LEVEL should be 1 .. 22 (default 15).
lzma:
(no options) (deprecated - no kernel support)
ENVIRONMENT
SOURCE_DATE_EPOCH
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.
EXAMPLES
mksquashfs DIRECTORY IMAGE.SQFS
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.
mksquashfs DIRECTORY FILE1 FILE2 IMAGE.SQFS
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.
mksquashfs DIRECTORY IMAGE.SQFS -b 1M -comp zstd
Use a block size of 1 Mbyte and Zstandard compression to create the filesystem.
mksquashfs DIRECTORY IMAGE.SQFS -e file1 file2
Exclude file1 and file2 from DIRECTORY when creating filesystem. No wildcard
matching of files.
mksquashfs DIRECTORY IMAGE.SQFS -wildcards -e "*.gz"
Exclude anything in DIRECTORY which matches the wildcard pattern "*.gz".
mksquashfs DIRECTORY IMAGE.SQFS -wildcards -e "... *.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.
Using pseudo file definitions
mksquashfs DIRECTORY IMAGE.SQFS -p "build_dir d 0644 0 0"
Create a directory called "build_dir" in the output filesystem.
mksquashfs DIRECTORY IMAGE.SQFS -p "version.txt l /tmp/build/version"
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.
mksquashfs DIRECTORY IMAGE.SQFS -p "date.txt f 0644 0 0 date"
Create a file called "date.txt" which holds the output (stdout) from running the
"date" command.
mksquashfs DIRECTORY IMAGE.SQFS -p "\"hello world\" f 0644 0 0 date"
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.
mksquashfs - IMAGE.SQFS -p "input f 0644 root root dd if=/dev/sda1 bs=1024" -p "/ d 0644 0
0"
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.
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.
Using Actions to not compress, change attributes etc.
mksquashfs DIRECTORY IMAGE.SQSH -action "uncompressed @ (name(*.jpg) || name(*.mpg) ) ||
(name(*.img) && filesize(+1G))"
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.
mksquashfs DIRECTORY IMAGE.SQSH -action "chmod(o+r)@! perm(o+r)"
If any files within DIRECTORY are not readable by "others", then make them readable
by others in the Squashfs filesystem.
mksquashfs DIRECTORY IMAGE.SQSH -action "uid(phillip)@! perm(o+r)"
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.
mksquashfs DIRECTORY IMAGE.SQSH -action "prune @ type(l) && ! exists"
Delete any symbolic link within DIRECTORY which points outside of DIRECTORY, i.e.
will be unresolvable in the Squashfs filesystem.
mksquashfs DIRECTORY IMAGE.SQSH -action "exclude @ depth(3)"
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.
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.
AUTHOR
Written by Phillip Lougher <phillip@squashfs.org.uk>
COPYRIGHT
Copyright © 2022 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
unsquashfs(1), sqfstar(1), sqfscat(1)
The README for the Squash-tools 4.5.1 release, describing the new features can be read
here https://github.com/plougher/squashfs-tools/blob/master/README-4.5.1
The Squashfs-tools USAGE guide can be read here
https://github.com/plougher/squashfs-tools/blob/master/USAGE
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