Ubuntu Manpage: genext2fs - ext2 filesystem generator for embedded systems

NAME

       genext2fs - ext2 filesystem generator for embedded systems

SYNOPSIS

       genext2fs [ options ] [ output-image ]

DESCRIPTION

       genext2fs  generates  an  ext2 filesystem as a normal (non-root) user. It does not require
       you to mount the image file to copy files on it, nor does it require that you  become  the
       superuser to make device nodes.

       The  filesystem  is  created  either  from  scratch,  or  from  an already existing one if
       specified by the -x option. Then each -d and -D option successively adds a "layer" to  the
       image.

       The  filesystem image is created in the file output-image. If not specified, it is sent to
       stdout.

       By default, the maximum number of inodes in the filesystem is the minimum number  required
       to  accommodate  the initial contents.  In this way, a minimal filesystem (typically read-
       only) can be created with minimal free inodes.  If required, free inodes can be  added  by
       passing  the  relevant  options.   The filesystem image size in blocks can be minimised by
       trial and error.

OPTIONS

-x, --starting-image image
Use this image as a starting point.

-d, --root directory[:path]
Add the given directory and contents at a particular path (by default the root).

-D, --devtable spec-file[:path]
Use spec-file to specify inodes to be added, at the given path (by default the
root), including files, directories and special files like devices. If the
specified files are already present in the image, their ownership and permission
modes will be adjusted accordingly (this can only occur when the -D option appears
after the options that create the specified files). Furthermore, you can use a
single table entry to create many devices with a range of minor numbers (see
examples below). All specified inodes receive the mtime of spec-file itself.

-a, --tarball file[:path]
Add the given archive (tarball) contents at a particular path (by default the
root). Note: if not compiled with `libarchive`, genext2fs will use a builtin
tarball parser with very primitive capabilities (e.g. no sparse file support,
generally no support other than for modern GNU tar without fancy options).

-b, --size-in-blocks blocks
Size of the image in blocks.

-B, --block-size bytes
Size of a filesystem block in bytes.

-N, --number-of-inodes inodes
Maximum number of inodes.

-L, --volume-label name
Set the volume label for the filesystem.

-i, --bytes-per-inode ratio
Used to calculate the maximum number of inodes from the available blocks.

-m, --reserved-percentage N
Number of reserved blocks as a percentage of size. Reserving 0 blocks will prevent
creation of the "lost+found" directory.

-o, --creator-os name
Value for creator OS field in superblock.

-g, --block-map path
Generate a block map file for this path.

-e, --fill-value value
Fill unallocated blocks with value.

-z, --allow-holes
Make files with holes.

-f, --faketime
Use a timestamp of 0 for inode and filesystem creation, instead of the present.
Useful for testing. See also SOURCE_DATE_EPOCH.

-q, --squash
Squash permissions and owners (same as -P -U).

-U, --squash-uids
Squash ownership of inodes added using the -d option, making them all owned by
root:root.

-P, --squash-perms
Squash permissions of inodes added using the -d option. Analogous to "umask 077".

-v, --verbose
Print resulting filesystem structure.

-V, --version
Print genext2fs version.

-h, --help
Display help.

ENVIRONMENT

       SOURCE_DATE_EPOCH
              Standardized   date   for   reproducible    builds,    see    https://reproducible-
              builds.org/docs/source-date-epoch/ for more information.

EXAMPLES

       genext2fs -b 1440 -d src /dev/fd0

       All files in the src directory will be written to /dev/fd0 as a new ext2 filesystem image.
       You can then mount the floppy as usual.

       genext2fs -b 1024 -d src -D device_table.txt flashdisk.img

       This example builds a filesystem from all the files in src, then device nodes are  created
       based  on the contents of the file device_table.txt.  Entries in the device table take the
       form of:

       <name> <type> <mode> <uid> <gid> <major> <minor> <start> <inc> <count>

       where name is the file name and type can be one of:
              f    A regular file
              d    Directory
              c    Character special device file
              b    Block special device file
              p    Fifo (named pipe)
              l    Symbolic link
       uid is the user id for the target file, gid is the group id for the target file.  The rest
       of the entries (major, minor, etc) apply only to device special files.

       An example device file follows:

              # name    type mode uid gid major minor start inc count

              /dev      d    755  0    0    -    -    -    -    -
              /dev/mem  c    640  0    0    1    1    0    0    -
              /dev/tty  c    666  0    0    5    0    0    0    -
              /dev/tty  c    666  0    0    4    0    0    1    6
              /dev/loop b    640  0    0    7    0    0    1    2
              /dev/hda  b    640  0    0    3    0    0    0    -
              /dev/hda  b    640  0    0    3    1    1    1    16
              /dev/log  s    666  0    0    -    -    -    -    -

       This  device  table creates the /dev directory, a character device node /dev/mem (major 1,
       minor 1), and also creates /dev/tty, /dev/tty[0-5], /dev/loop[0-1], /dev/hda, /dev/hda1 to
       /dev/hda15 and /dev/log socket.

AUTHOR

       This  manual  page  was  written  by  David  Kimdon  <dwhedon@debian.org>,  for the Debian
       GNU/Linux system (but may  be  used  by  others).   Examples  provided  by  Erik  Andersen
       <andersen@codepoet.org>.

                                         August 19, 2006                             GENEXT2FS(8)