[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.

[Examples]
.TP
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.
.TP
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.
.TP
sqfstar -b 1M -comp zstd IMAGE.SQFS < archive.tar
Use a block size of 1 Mbyte and Zstandard compression to create the filesystem. 
.TP
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.
.TP
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).
.TP
sqfstar IMAGE.SQFS file1 file2 < archive.tar
Exclude file1 and file2 from the tar file when creating filesystem.
.TP
sqfstar IMAGE.SQFS "*.gz" < archive.tar
Exclude any files in the top level directory which matches the wildcard pattern
"*.gz".
.TP
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.
.PP
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.

.SS Using pseudo file definitions
.TP
sqfstar -p "build_dir d 0644 0 0" IMAGE.SQFS < archive.tar
Create a directory called "build_dir" in the output filesystem.
.TP
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.
.TP
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.
.TP
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.
.TP
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.
.PP
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.