Provided by: squashfs-tools_2.2r2-2ubuntu2_i386
mksquashfs - Create or modify a Squash file system
mksquashfs source... dest [options] [-e list of exclude dirs/files]
A squashfs is a compressed read-only file system. Use the mksquashfs
program to create a new squashed file system, and to append new data to
an existing squashed file system.
If a single source directory is specified (i.e. mksquashfs source
output_fs), the squashfs filesystem will consist of that directory,
with the top-level root directory corresponding to the source
If multiple source directories or files are specified, mksquashfs will
merge the specified sources into a single filesystem, with the root
directory containing each of the source files/directories. The name of
each directory entry will be the basename of the source path. If more
than one source entry maps to the same name, the conflicts are named
xxx_1, xxx_2, etc. where xxx is the original name.
The dest argument can either be a conventional file or a block device.
If the file doesn’t exist it will be created, if it does exist and a
squashfs filesystem exists on it, mksquashfs will append. The -noappend
option will write a new filesystem irrespective of whether an existing
filesystem is present.
There are a large number of options that can be used to control the
compression in mksquashfs. By and large the defaults are the most
optimum settings and should only be changed in exceptional
The -noI, -noD and -noF options (also -noInodeCompression,
-noDataCompression and -noFragmentCompression) can be used to force
mksquashfs to not compress inodes/directories, data and fragments
respectively. Giving all options generates an uncompressed filesystem.
By default files in the generated filesystem inherit the UID and GID
ownership of the original file. However, mksquashfs provides a number
of options which can be used to override the ownershipÂ :
· The options -all-root and -root-owned (both do exactly the same
thing) force all file uids/gids in the generated Squashfs filesystem
to be root. This allows root owned filesystems to be built without
root access on the host machine.
· The -force-uid uid option forces all files in the generated Squashfs
filesystem to be owned by the specified uid. The uid can be
specified either by name (i.e. root) or by number.
· The -force-gid gid option forces all files in the generated Squashfs
filesystem to be group owned by the specified gid. The gid can be
specified either by name (i.e. root) or by number.
The -e and -ef options allow files/directories to be specified which
are excluded from the output filesystem. The -e option takes the
exclude files/directories from the command line, the -ef option takes
the exlude files/directories from the specified exclude file, one
file/directory per line. If an exclude file/directory is absolute (i.e.
prefixed with /, ../, or ./) the entry is treated as absolute, however,
if an exclude file/directory is relative, it is treated as being
relative to each of the sources in turn, i.e. mksquashfs /tmp/source1
source2 output_fs -e ex1 /tmp/source1/ex2 out/ex3 Will generate exclude
files /tmp/source1/ex2, /tmp/source1/ex1, source2/ex1,
/tmp/source1/out/ex3 and source2/out/ex3.
The -e and -ef exclude options are usefully used in archiving the
entire filesystem, where it is wished to avoid archiving /proc, and the
filesystem being generated, i.e. mksquashfs / /tmp/root.sqsh -e proc
Multiple -ef options can be specified on the command line, and the -ef
option can be used in conjuction with the -e option.
The -info option displays the files/directories as they are compressed
and added to the filesystem. The original uncompressed size of each
file is printed, along with DUPLICATE if the file is a duplicate of a
file in the filesystem.
The -le and -be options can be used to force mksquashfs to generate a
little endian or big endian filesystem. Normally mksquashfs will
generate a filesystem in the host byte order. Squashfs, for
portability, will mount different ordered filesystems (i.e. it can
mount big endian filesystems running on a little endian machine), but
these options can be used for greater optimisation.
print version, licence and copyright message.
-info print files written to filesystem
set data block to block_size. This can be either 4096, 8192,
16384, 32768 or 65536 bytes. Default is 65536 bytes
-2.0 create a 2.0 filesystem
-noI or -noInodeCompression
do not compress inode table
do not compress data blocks
-noF or -noFragmentCompression
do not compress fragment blocks
do not use fragmentsÂ : tells mksquashfs to not generate
fragment blocks, and rather generate a filesystem similar to a
SquashfsÂ 1.x filesystem. It will of course still be a
SquashfsÂ 2.0 filesystem but without fragments, and so it won’t
be mountable on a SquashfsÂ 1.x system.
use fragment blocks for files larger than block sizeÂ : tells
mksquashfs to always generate fragments for files irrespective
of the file length. By default only small files less than the
block size are packed into fragment blocks. The ends of files
which do not fit fully into a block, are NOT by default packed
into fragments. To illustrate this, a 100K file has an initial
64K block and a 36K remainder. This 36K remainder is not packed
into a fragment by default. This is because to do so leads to a
10 - 20% drop in sequential I/O performance, as a disk head seek
is needed to seek to the initial file data and another disk seek
is need to seek to the fragment block. Specify this option if
you want file remainders to be packed into fragment blocks.
Doing so may increase the compression obtained BUT at the
expense of I/O speed.
do not perform duplicate checkingÂ : tells mksquashfs to not
check the files being added to the filesystem for duplicates.
This can result in quicker filesystem generation and appending
although obviously compression will suffer badly if there is a
lot of duplicate files.
do not append to existing filesystem
if one source directory is specified, create a root directory
containing that directory, rather than the contents of the
when appending source files/directories, make the original root
become a subdirectory in the new root called name, rather than
adding the new source items to the original root
-all-root or -root-owned
make all files owned by root
set all file uids to uid
set all file gids to gid
-le create a little endian filesystem
-be create a big endian filesystem
-nopad do not pad filesystem to a multiple of 4KÂ : This is performed
by default to enable the output filesystem file to be mounted by
loopback, which requires files to be a 4K multiple. If the
filesystem is being written to a block device, or is to be
stored in a bootimage, the extra pad bytes are not needed.
add checkdata for greater filesystem checks
sort files according to priorities in sort_file. One file or dir
with priority per line. Priority -32768 to 32767, default
-e list of exclude dirs/files
inline list of files / directories to exclude
file containing a list of files / directories to exclude, one
For following examples, take two example directoriesÂ :
· Source directory /home/phillip/test contains file1, file2 and dir1.
· Source directory goodies contains goodies1, goodies2 and goodies3.
mksquashfs /home/phillip/test output_fs
This will generate a squashfs filesystem with root entries
file1, file2 and dir1.
mksquashfs /home/phillip/test goodies output_fs
This will create a squashfs filesystem with the root containing
entries test and goodies corresponding to the source directories
/home/phillip/test and goodies.
mksquashfs /home/phillip/test goodies test output_fs
This is the same as the previous example, except a third source
directory test has been specified. This conflicts with the first
directory named test and will be renamed test_1.
Multiple sources allow filesystems to be generated without
needing to copy all source files into a common directory. This
simplifies creating filesystems.
mksquashfs /home/phillip/test output_fs -keep-as-directory
This is the same as the first example, except for
-keep-as-directory. This will generate a root directory
containing directory test, rather than the test directory
contents file1, file2 and dir1.
Squashfs was written by Phillip Lougher
<email@example.com>, in Chepstow, Wales, UK. If you like
the program, or have any problems, then please email me, as it’s nice
to get feedback !
This manual page was written by FrÃ©dÃ©ric Boiteux
<firstname.lastname@example.org> for the Debian system (but may be used by
others) using the SquashFS HOWTO from Artemiy I. Pavlov and squashfs’s
README file. Permission is granted to copy, distribute and/or modify
this document under the terms of the GNU General Public License,
Version 2 any later version published by the Free Software Foundation.
On Debian systems, the complete text of the GNU General Public License
can be found in /usr/share/common-licenses/GPL.
december 20, 2004 MKSQUASHFS(8)