sqfstar - Man Page

tool to create a squashfs filesystem from a tar archive

Examples (TL;DR)

Create a squashfs filesystem (compressed using gzip by default) from an uncompressed tar archive: sqfstar filesystem.squashfs < archive.tar
Create a squashfs filesystem from a tar archive compressed with gzip, and [comp]ress the filesystem using a specific algorithm: zcat archive.tar.gz | sqfstar -comp gzip|lzo|lz4|xz|zstd|lzma filesystem.squashfs
Create a squashfs filesystem from a tar archive compressed with xz, excluding some of the files: xzcat archive.tar.xz | sqfstar filesystem.squashfs file1 file2 ...
Create a squashfs filesystem from a tar archive compressed with zstd, excluding files ending with .gz: zstdcat archive.tar.zst | sqfstar filesystem.squashfs "*.gz"
Create a squashfs filesystem from a tar archive compressed with lz4, excluding files matching a regular expression: lz4cat archive.tar.lz4 | sqfstar filesystem.squashfs -regex "regular_expression"

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 suffix 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 directories. 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.
-xattrs: store extended attributes (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.
-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 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 (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 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, 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

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 running 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 wildcard 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 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 examples), to ensure that they are passed to Mksquashfs as a single argument, and to ensure that they are not processed by the shell.