MKE2FS(8) MKE2FS(8)
NAME
mke2fs - create an ext2/ext3 filesystem
SYNOPSIS
mke2fs [ -c | -l filename ] [ -b block-size ] [ -f fragment-size ] [ -g blocks-per-group ]
[ -i bytes-per-inode ] [ -j ] [ -J journal-options ] [ -N number-of-inodes ] [ -n ] [ -m
reserved-blocks-percentage ] [ -o creator-os ] [ -O feature[,...] ] [ -q ] [ -r fs-revi-
sion-level ] [ -E extended-options ] [ -v ] [ -F ] [ -L volume-label ] [ -M last-mounted-
directory ] [ -S ] [ -T filesystem-type ] [ -V ] device [ blocks-count ]
mke2fs -O journal_dev [ -b block-size ] [ -L volume-label ] [ -n ] [ -q ] [ -v ] external-
journal [ blocks-count ]
DESCRIPTION
mke2fs is used to create an ext2/ext3 filesystem (usually in a disk partition). device is
the special file corresponding to the device (e.g /dev/hdXX). blocks-count is the number
of blocks on the device. If omitted, mke2fs automagically figures the file system size.
If called as mkfs.ext3 a journal is created as if the -j option was specified.
OPTIONS
-b block-size
Specify the size of blocks in bytes. Valid block size vales are 1024, 2048 and
4096 bytes per block. If omitted, mke2fs block-size is hueristically determined by
the file system size and the expected usage of the filesystem (see the -T option).
If block-size is negative, then mke2fs will use heuristics to determine the appro-
priate block size, with the constraint that the block size will be at least block-
size bytes. This is useful for certain hardware devices which require that the
blocksize be a multiple of 2k.
-c Check the device for bad blocks before creating the file system. If this option is
specified twice, then a slower, destructive, read-write test is used instead of a
fast read-only test.
-E extended-options
Set extended options for the filesystem. Extended options are comma separated, and
may take an argument using the equals ('=') sign. The -E option used to be -R in
earlier versions of mke2fs. The -R option is still accepted for backwards compati-
bility. The following extended options are supported:
stride=stripe-size
Configure the filesystem for a RAID array with stripe-size filesystem
blocks per stripe.
resize=max-online-resize
Reserve enough space so that the block group descriptor table can grow
to support a filesystem that has max-online-resize blocks.
-f fragment-size
Specify the size of fragments in bytes.
-F Force mke2fs to run, even if the specified device is not a block special device, or
appears to be mounted.
-g blocks-per-group
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 stride RAID parameter as part of the -R option rather than manipulating
the number of blocks per group.) This option is generally used by developers who
are developing test cases.
-i bytes-per-inode
Specify the bytes/inode ratio. mke2fs creates an inode for every bytes-per-inode
bytes of space on the disk. The larger the bytes-per-inode 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.
-j Create the filesystem with an ext3 journal. If the -J 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.
-J journal-options
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:
size=journal-size
Create an internal journal (i.e., stored inside the filesystem) of size
journal-size megabytes. 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.
device=external-journal
Attach the filesystem to the journal block device located on external-
journal. The external journal must already have been created using the
command
mke2fs -O journal_dev external-journal
Note that external-journal must have been created with the same block
size as the new filesystem.
Instead of specifying a device name directly, external-journal can also
be specified by either LABEL=label or UUID=UUID to locate the external
journal by either the volume label or UUID stored in the ext2
superblock at the start of the journal. Use dumpe2fs(8) to display a
journal device's volume label and UUID. See also the -L option of
tune2fs(8).
Only one of the size or device options can be given for a filesystem.
-l filename
Read the bad blocks list from filename. 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 -c option to mke2fs is a much simpler and less error-prone method of
checking a disk for bad blocks before formatting it, as mke2fs will automatically
pass the correct parameters to the badblocks program.
-L Set the volume label for the filesystem.
-m reserved-blocks-percentage
Specify the percentage of the filesystem blocks reserved for the super-user. This
value defaults to 5%.
-M 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
filesytem should be mounted.
-n 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 -n option added, of course!)
-N number-of-inodes
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 the bytes-per-inode
ratio). This allows the user to specify the number of desired inodes directly.
-o creator-os
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 of the mke2fs exe-
cutable.
-O feature[,...]
Create filesystem with given features (filesystem options). Features which are
normally turned on by default may be disabled by prefixing the feature with a caret
('^') symbol. Currently, the sparse_super and filetype features are turned on by
default when mke2fs is run on a system with Linux 2.2 or later (unless creator-os
is set to the Hurd). Filesystems that may need to be mounted on pre-2.2 Linux or
other kernels should be created with -O none (or -r 0 for Linux 1.2) which will
disable these features, even if mke2fs is run on a system which can support them.
The following filesystem options are supported:
dir_index
Use hashed b-trees to speed up lookups in large directories.
filetype
Store file type information in directory entries.
has_journal
Create an ext3 journal (as if using the -j option).
journal_dev
Create an external ext3 journal on the given device instead of a regu-
lar ext2 filesystem. Note that external-journal must be created with
the same block size as the filesystems that will be using it.
sparse_super
Create a filesystem with fewer superblock backup copies (saves space on
large filesystems).
-q Quiet execution. Useful if mke2fs is run in a script.
-r revision
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.
-S 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 mke2fs to reinitialize the superblock and group descriptors,
while not touching the inode table and the block and inode bitmaps. The e2fsck
program should be run immediately after this option is used, and there is no guar-
antee 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.
-T fs-type
Specify how the filesystem is going to be used, so that mke2fs can chose optimal
filesystem parameters for that use. The supported filesystem types are:
news one inode per 4kb block
largefile one inode per megabyte
largefile4 one inode per 4 megabytes
-v Verbose execution.
-V Print the version number of mke2fs and exit.
AUTHOR
This version of mke2fs has been written by Theodore Ts'o <>.
BUGS
mke2fs accepts the -f 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.
AVAILABILITY
mke2fs is part of the e2fsprogs package and is available from http://e2fsprogs.source-
forge.net.
SEE ALSO
badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8)
E2fsprogs version 1.35 February 2004 MKE2FS(8)
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