Provided by: squashfs-tools-ng_1.1.4-1_amd64 
NAME
tar2sqfs - create a SquashFS image from a tar archive
SYNOPSIS
tar2sqfs [OPTIONS...] <sqfsfile>
DESCRIPTION
Quickly and painlessly turn a tar ball into a SquashFS filesystem image.
By default, the program reads the archive from standard input. Compressed archives are
supported.
Possible options:
--root-becomes, -r <dir>
If set, only pack entries that are underneath the specified directory. The prefix
is stripped and the meta data for the directory itself is copied to the root inode
(i.e. the ownership, permissions, extended attributes, modification time).
If this option is not set, tar2sqfs implicitly treats ./ or absolute paths this
way, i.e. if the archive contains an entry for ./, it becomes the root node and the
prefix is stripped from all paths (and similar for absolute paths and /).
--no-symlink-retarget, -S
If --root-becomes is used, link targets are adjusted if they are prefixed by the
root path. By default, this is also done on symbolic links, that have a target that
is prefixed by the root path and they are converted to aboluste paths with the
prefix removed. However, because symlinks can point across mount points, this may
actually be intended for some use cases.
This flag allows changing the default behaviour, so only hard links are retargeted.
--compressor, -c <name>
Select the compressor to use. Run tar2sqfs --help to get a list of all available
compressors and the default selection.
--comp-extra, -X <options>
A comma separated list of extra options for the selected compressor. Specify help
to get a list of available options.
--num-jobs, -j <count>
If libsquashfs was compiled with a thread pool based, parallel data compressor,
this option can be used to set the number of compressor threads. If not set, the
default is the number of available CPU cores.
--queue-backlog, -Q <count>
Maximum number of data blocks in the thread worker queue before the packer starts
waiting for the block processors to catch up. Higher values result in higher memory
consumption. Defaults to 10 times the number of workers.
--block-size, -b <size>
Block size to use for SquashFS image. Defaults to 131072.
--dev-block-size, -B <size>
Device block size to padd the image to. Defaults to 4096.
--defaults, -d <options>
A comma separated list of default values for implicitly created directories. The
following values can be set:
┌──────────────┬────────────────────────────────────────┐
│Option │ Default │
├──────────────┼────────────────────────────────────────┤
│uid=<value> │ 0 │
├──────────────┼────────────────────────────────────────┤
│gid=<value> │ 0 │
├──────────────┼────────────────────────────────────────┤
│mode=<value> │ 0755 │
├──────────────┼────────────────────────────────────────┤
│mtime=<value> │ $SOURCE_DATE_EPOCH if set, 0 otherwise │
└──────────────┴────────────────────────────────────────┘
--no-keep-time, -k
Replace the time stamps from the tar archive with default time stamps for all
entries.
The default behavior is to preserve the time stamps from the archive to the extent
possible (SquashFS has second resolution and 32 bit time stamps; tar can use
extensions to specify much larger timestamps with arbitrary precision). The root
inode (unless --root-becomes is used) and the modification time on the SquashFS
image itself will still be set to defaults.
--no-xattr, -x
Do not copy extended attributes from archive. Default behaviour is to copy all
extended attributes and skip the ones that cannot be encoded in SquashFS.
--no-skip, -s
Abort if a tar record cannot be read instead of skipping it.
--exportable, -e
Generate an export table for NFS support.
--no-tail-packing, -T
Do not perform tail end packing on files that are larger than the specified block
size.
--force, -f
Overwrite the output file if it exists.
--quiet, -q
Do not print out progress reports.
--help, -h
Print help text and exit.
--version, -V
Print version information and exit.
COMPATIBILITY
Currently the program can process v7 format, pre-POSIX ustar, POSIX tar and GNU tar
archives. PAX extension headers are also supported. Global PAX headers are ignored.
The support for GNU tar is limited to a commonly used subset (i.e. some legacy extensions
that GNU tar itself no longer generates are not supported; neither are multi volume
archives).
The input tar file can either be uncompressed, or stream compressed using gzip, xz, zstd
or bzip2. The program transparently auto-detects and unpacks any stream compressed
archive. The exact list of supported compressors depends on the compile configuration.
Extended attributes are supported through the SCHILY.xattr extension (favoured by GNU tar
and star) or through the LIBARCHIVE.xattr extension.
If any unsupported section or extended attribute key is encountered in an archive, a
warning message is written to stderr. If the --no-skip option is set, processing aborts.
By default, unknown sections and unsupported extended attributes are simply skipped after
issuing a warning.
ENVIRONMENT
If the command line switch --defaults is not used or no default mtime is specified, the
value of the environment variable SOURCE_DATE_EPOCH is used for all file and filesystem
timestamps.
If SOURCE_DATE_EPOCH is not set, not a parsable number or it is out of range, the
timestamps default to 0.
Environment variables are only used if no explicit command line switches are set. Explicit
command line switches are always preferred over the environment variables.
EXAMPLES
Turn an uncompressed tar archive into a SquashFS image:
tar2sqfs rootfs.sqfs < rootfs.tar.gz
SEE ALSO
gensquashfs(1), rdsquashfs(1), sqfs2tar(1)
AUTHOR
Written by David Oberhollenzer.
COPYRIGHT
Copyright © 2019 David Oberhollenzer License GPLv3+: GNU GPL version 3 or later
<https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY,
to the extent permitted by law.