SQFSTAR(1) User Commands SQFSTAR(1)
NAME
sqfstar - tool to create a squashfs filesystem from a tar archive
SYNOPSIS
cat xxx.tar | sqfstar [OPTIONS] FILESYSTEM [exclude files]
zcat xxx.tgz | sqfstar [OPTIONS] FILESYSTEM [exclude files]
xzcat xxx.tar.xz | sqfstar [OPTIONS] FILESYSTEM [exclude files]
zstdcat xxx.tar.zst | sqfstar [OPTIONS] FILESYSTEM [exclude 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 con-
strained block device/memory systems (e.g. embedded systems) where low
overhead is needed.
OPTIONS
Filesystem compression options:
-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 re-
spectively.
-comp COMP
select COMP compression. Compressors available: gzip (default),
lzo, lz4, xz, zstd, lzma.
-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-compression
do not compress any of the data or metadata. This is equivalent
to specifying -noI -noD -noF and -noX.
Filesystem build options:
-reproducible
build filesystems that are reproducible (default).
-not-reproducible
build filesystems that are not reproducible.
-mkfs-time TIME
set filesystem creation timestamp to TIME. TIME can be an un-
signed 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 recog-
nises can be used such as "now", "last week", or "Wed Feb 15
21:02:39 GMT 2023".
-all-time TIME
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".
-root-time TIME
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".
-root-mode MODE
set root directory permissions to octal MODE.
-root-uid VALUE
set root directory owner to specified VALUE, VALUE can be either
an integer uid or user name.
-root-gid VALUE
set root directory group to specified VALUE, VALUE can be either
an integer gid or group name.
-all-root
make all files owned by root.
-force-uid VALUE
set all file uids to specified VALUE, VALUE can be either an in-
teger uid or user name.
-force-gid VALUE
set all file gids to specified VALUE, VALUE can be either an in-
teger gid or group name.
-default-mode MODE
tar files often do not store permissions for intermediate direc-
tories. This option sets the default directory permissions to
octal MODE, rather than 0755. This also sets the root inode
mode.
-default-uid UID
tar files often do not store uids for intermediate directories.
This option sets the default directory owner to UID, rather than
the user running Sqfstar. This also sets the root inode uid.
-default-gid GID
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 Sqfstar. This also sets the root
inode gid.
-pseudo-override
make pseudo file uids and gids override -all-root, -force-uid
and -force-gid options.
-exports
make the filesystem exportable via NFS.
-no-sparse
do not detect sparse files.
-no-fragments
do not use fragments.
-no-tailends
do not pack tail ends into fragments.
-no-duplicates
do not perform duplicate checking.
-no-hardlinks
do not hardlink files, instead store duplicates.
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.
-ef EXCLUDE_FILE
list of exclude dirs/files. One per line.
-regex allow POSIX regular expressions to be used in exclude
dirs/files.
-ignore-zeros
allow tar files to be concatenated together and fed to Sqfstar.
Normally a tarfile has two consecutive 512 byte blocks filled
with zeros which means EOF and Sqfstar will stop reading after
the first tar file on encountering them. This option makes Sqfs-
tar ignore the zero filled blocks.
Filesystem extended attribute (xattrs) options:
-no-xattrs
do not store extended attributes.
-xattrs
store extended attributes (default).
-xattrs-exclude REGEX
exclude any xattr names matching REGEX. REGEX is a POSIX regu-
lar 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 regu-
lar expression, e.g. -xattrs-include '^user.' includes xattrs
from the user namespace.
-xattrs-add NAME=VAL
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 en-
coded, or prefixed with 0x, where val will be treated as hex-
idecimal. 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.
Sqfstar runtime options:
-version
print version, licence and copyright message.
-force force Sqfstar to write to block device or file.
-exit-on-error
treat normally ignored errors as fatal.
-quiet no verbose output.
-info print files written to filesystem.
-no-progress
do not display the progress bar.
-progress
display progress bar when using the -info option.
-percentage
display a percentage rather than the full progress bar. Can be
used with dialog --gauge etc.
-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 Sqfstar.
-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 Sqfstar (alterna-
tive to -throttle).
-processors NUMBER
use NUMBER processors. By default will use number of processors
available.
-mem SIZE
use SIZE physical memory for caches. Use K, M or G to specify
Kbytes, Mbytes or Gbytes respectively.
-mem-percent PERCENT
use PERCENT physical memory for caches. Default 25%.
-mem-default
print default memory usage in Mbytes.
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:
-fstime TIME
alternative name for mkfs-time.
-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 x name=val"
create an extended attribute.
-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, fil-
tered, 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 fil-
ters: 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 ab-
solute value. The dictionary size must be less than or equal to
the block size and 8192 bytes or larger. It must also be stor-
able 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://repro-
ducible-builds.org/docs/source-date-epoch/ for more information.
EXAMPLES
sqfstar IMAGE.SQFS < archive.tar
Create a Squashfs filesystem from the uncompressed tar file
"archive.tar". Sqfstar will use the default compressor (nor-
mally gzip), and block size of 128 Kbytes.
zcat archive.tgz | sqfstar IMAGE.SQFS
Create a Squashfs filesystem from the compressed tar file
"archive.tgz". Sqfstar will use the default compressor (normally
gzip), and block size of 128 Kbytes.
sqfstar -b 1M -comp zstd IMAGE.SQFS < archive.tar
Use a block size of 1 Mbyte and Zstandard compression to create
the filesystem.
sqfstar -root-uid 0 -root-gid 0 IMAGE.SQFS < archive.tar
Tar files do not supply a definition for the root directory, and
the default is to make the directory owned/group owned by the
user running Sqfstar. The above command sets the owner-
ship/group ownership to root.
sqfstar -root-mode 0755 IMAGE.SQFS < archive.tar
The default permissions for the root directory is 0777 (rwxr-
wxrwx). The above command sets the permissions to 0755 (rwxr-
xr-x).
sqfstar IMAGE.SQFS file1 file2 < archive.tar
Exclude file1 and file2 from the tar file when creating filesys-
tem.
sqfstar IMAGE.SQFS "*.gz" < archive.tar
Exclude any files in the top level directory which matches the
wildcard pattern "*.gz".
sqfstar IMAGE.SQFS "... *.gz" < archive.tar
Exclude any file which matches the wildcard pattern "*.gz" any-
where within the tar file. The initial "..." indicates the
wildcard pattern is "non-anchored" and will match anywhere.
Note: when passing wildcarded names to Sqfstar, they should be quoted
(as in the above examples), to ensure that they are not processed by
the shell.
Using pseudo file definitions
sqfstar -p "build_dir d 0644 0 0" IMAGE.SQFS < archive.tar
Create a directory called "build_dir" in the output filesystem.
sqfstar -p "version.txt l /tmp/build/version" IMAGE.SQFS < archive.tar
Create a reference called "version.txt" to a file not in the tar
archive, which acts as if that file was in the tar archive.
sqfstar -p "date.txt f 0644 0 0 date" IMAGE.SQFS < archive.tar
Create a file called "date.txt" which holds the output (stdout)
from running the "date" command.
sqfstar -p "\"hello world\" f 0644 0 0 date" IMAGE.SQFS < archive.tar
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.
sqfstar -p "input f 0644 root root dd if=/dev/sda1 bs=1024" IMAGE.SQFS
< archive.tar
Create a file containing the contents of partition /dev/sda1".
The above allows input from these special files to be captured
and placed in the Squashfs filesystem.
Note: pseudo file definitions should be quoted (as in the above exam-
ples), to ensure that they are passed to Mksquashfs as a single argu-
ment, and to ensure that they are not processed by the shell.
AUTHOR
Written by Phillip Lougher <phillip@squashfs.org.uk>
COPYRIGHT
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 MER-
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
SEE ALSO
mksquashfs(1), unsquashfs(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
sqfstar version 4.6.1 April 2024 SQFSTAR(1)
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