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 constrained 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 suf- fix of K or M can be given to specify Kbytes or Mbytes respectively. -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 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". -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 integer uid or user name. -force-gid VALUE set all file gids to specified VALUE, VALUE can be either an integer gid or group name. -default-mode MODE tar files often do not store permissions for intermediate directo- ries. 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 Sqfstar ignore the zero filled blocks. Filesystem extended attribute (xattrs) options: -no-xattrs do not store extended attributes (default). -xattrs store extended attributes (unsupported). -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. -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 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 en- coding, except backslashes are specially treated, and a backslash followed by 3 octal digits can be used to encode any ASCII charac- ter, which obviously can be used to encode control codes. The op- tion 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 (alternative 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 suf- fix 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, filtered, huff- man_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://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 (normally 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 run- ning Sqfstar. The above command sets the ownership/group ownership to root. sqfstar -root-mode 0755 IMAGE.SQFS < archive.tar The default permissions for the root directory is 0777 (rwxrwxrwx). 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 filesystem. sqfstar IMAGE.SQFS "*.gz" < archive.tar Exclude any files in the top level directory which matches the wild- card pattern "*.gz". sqfstar IMAGE.SQFS "... *.gz" < archive.tar Exclude any file which matches the wildcard pattern "*.gz" anywhere within the tar file. The initial "..." indicates the wildcard pat- tern 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 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 (C) 2023 Phillip Lougher <phillip@squashfs.org.uk> This program is free software; you can redistribute it and/or modify it un- der the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later ver- sion. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FIT- NESS 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 fea- tures can be read here https://github.com/plougher/squashfs-tools/blob/mas- ter/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 August 2026 SQFSTAR(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | PSEUDO FILE DEFINITION FORMAT | COMPRESSORS AVAILABLE AND COMPRESSOR SPECIFIC OPTIONS | ENVIRONMENT | EXAMPLES | AUTHOR | COPYRIGHT | SEE ALSO
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