sqfstar - Man Page

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 build options

-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).

-exports

make the filesystem exportable via NFS.

-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-fragments

do not use fragments.

-no-tailends

don't pack tail ends into fragments.

-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.

Filesystem filter options

-ef EXCLUDE_FILE

list of exclude dirs/files.  One per line.

-regex

Allow POSIX regular expressions to be used in exclude dirs/files.

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

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.

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.

Author

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

See Also

mksquashfs(1), unsquashfs(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

Referenced By

mksquashfs(1), sqfscat(1), unsquashfs(1).

July 2022 sqfstar version 4.5.1