is used to create an ext2/ext3 filesystem (usually in a disk partition).
is the special file corresponding to the device (e.g
is the number of blocks on the device. If omitted,
automagically figures the file system size. If called as
a journal is created as if the
option was specified.
Specify the size of blocks in bytes. Valid block size vales are 1024,
2048 and 4096 bytes per block. If omitted,
block-size is heuristically determined by the file system size and
the expected usage of the filesystem (see the
is negative, then
will use heuristics to determine the
appropriate block size, with the constraint that the block size will be
bytes. This is useful for certain hardware devices which require that
the blocksize be a multiple of 2k.
Check the device for bad blocks before creating the file system. If
this option is specified twice, then a slower, read-write
test is used instead of a fast read-only test.
Set extended options for the filesystem. Extended options are comma
separated, and may take an argument using the equals ('=') sign. The
option used to be
in earlier versions of
option is still accepted for backwards compatibility. The
following extended options are supported:
Configure the filesystem for a RAID array with
filesystem blocks per stripe.
Reserve enough space so that the block group descriptor table can grow
to support a filesystem that has max-online-resize blocks.
Specify the size of fragments in bytes.
to run, even if the specified device is not a
block special device, or appears to be mounted.
Specify the number of blocks in a block group. There is generally no
reason the user to ever set this parameter, as the default is optimal
for the filesystem. (For administrators who are creating
filesystems on RAID arrays, it is preferable to use the
RAID parameter as part of the
option rather than manipulating the number of blocks per group.)
This option is generally used by developers who
are developing test cases.
Specify the bytes/inode ratio.
creates an inode for every
bytes of space on the disk. The larger the
ratio, the fewer inodes will be created. This value generally shouldn't
be smaller than the blocksize of the filesystem, since then too many
inodes will be made. Be warned that is not possible to expand the number
of inodes on a filesystem after it is created, so be careful deciding the
correct value for this parameter.
Create the filesystem with an ext3 journal. If the
option is not specified, the default journal parameters will be used to
create an appropriately sized journal (given the size of the filesystem)
stored within the filesystem. Note that you must be using a kernel
which has ext3 support in order to actually make use of the journal.
Create the ext3 journal using options specified on the command-line.
Journal options are comma
separated, and may take an argument using the equals ('=') sign.
The following journal options are supported:
Create an internal journal (i.e., stored inside the filesystem) of size
The size of the journal must be at least 1024 filesystem blocks
(i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
and may be no more than 102,400 filesystem blocks.
Attach the filesystem to the journal block device located on
journal must already have been created using the command
mke2fs -O journal_devexternal-journal
must have been created with the
same block size as the new filesystem.
In addition, while there is support for attaching
multiple filesystems to a single external journal,
the Linux kernel and
do not currently support shared external journals yet.
Instead of specifying a device name directly,
can also be specified by either
to locate the external journal by either the volume label or UUID
stored in the ext2 superblock at the start of the journal. Use
to display a journal device's volume label and UUID. See also the
Only one of the
size or device
options can be given for a filesystem.
Read the bad blocks list from
Note that the block numbers in the bad block list must be generated
using the same block size as used by mke2fs. As a result, the
is a much simpler and less error-prone method of checking a disk for bad
blocks before formatting it, as
will automatically pass the correct parameters to the
Set the volume label for the filesystem to
The maximum length of the
volume label is 16 bytes.
Specify the percentage of the filesystem blocks reserved for
the super-user. This avoids fragmentation, and allows root-owned
daemons, such as
to continue to function correctly after non-privileged processes are
prevented from writing to the filesystem. The default percentage
Set the last mounted directory for the filesystem. This might be useful
for the sake of utilities that key off of the last mounted directory to
determine where the filesystem should be mounted.
causes mke2fs to not actually create a filesystem, but display what it
would do if it were to create a filesystem. This can be used to
determine the location of the backup superblocks for a particular
filesystem, so long as the mke2fs parameters that were passed when the
filesystem was originally created are used again. (With the
option added, of course!)
overrides the default calculation of the number of inodes that should be
reserved for the filesystem (which is based on the number of blocks and
ratio). This allows the user to specify the number
of desired inodes directly.
Manually override the default value of the "creator os" field of the
filesystem. Normally the creator field is set by default to the native OS
Create filesystem with given features (filesystem options), overriding
the default filesystem options. The default features which are
enabled by default are specified by the
relation, either in the
section in the
configuration file, or in the subsection of the
section for the filesystem type as specified by the
option. The filesystem type-specific configuration setting found in
section will override the global default found in
The filesystem feature set will be further edited
using either the feature set specification specified by this option,
or if this option is not specified, by the
relation for the filesystem type being created, or in the
section of the configuration file.
The filesystem feature set is comprised of a list of features, separated
by commas, that are to be enabled. To disable a feature, simply
prefix the feature name with a caret ('^') character. The
pseudo-filesystem feature "none" will clear all filesystem features.
Use hashed b-trees to speed up lookups in large directories.
Store file type information in directory entries.
Create an ext3 journal (as if using the
Create an external ext3 journal on the given device
instead of a regular ext2 filesystem.
must be created with the same
block size as the filesystems that will be using it.
Reserve space so the block group descriptor table may grow in the future.
Useful for online resizing using
will attempt to reserve enough space so that the
filesystem may grow to 1024 times its initial size. This can be changed
Create a filesystem with fewer superblock backup copies
(saves space on large filesystems).
Quiet execution. Useful if
is run in a script.
Set the filesystem revision for the new filesystem. Note that 1.2
kernels only support revision 0 filesystems. The default is to
create revision 1 filesystems.
Write superblock and group descriptors only. This is useful if all of
the superblock and backup superblocks are corrupted, and a last-ditch
recovery method is desired. It causes
to reinitialize the
superblock and group descriptors, while not touching the inode table
and the block and inode bitmaps. The
program should be run immediately after this option is used, and there
is no guarantee that any data will be salvageable. It is critical to
specify the correct filesystem blocksize when using this option,
or there is no chance of recovery.
Specify how the filesystem is going to be used, so that
can choose optimal filesystem parameters for that use. The filesystem
types that are can be supported are defined in the configuration file
The default configuration file contains definitions for the filesystem
types: small, floppy, news, largefile, and largefile4.
Print the version number of
This version of
has been written by Theodore Ts'o <firstname.lastname@example.org>.
option but currently ignores it because the second
extended file system does not support fragments yet.
There may be other ones. Please, report them to the author.