From Linux Man Pages
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 ]
[ -I inode-size ] [ -j ] [ -J journal-options ] [ -N number-of-inodes ] [ -n ] [ -m reserved-blocks-percentage ]
[ -o creator-os ] [ -O feature[,...] ] [ -q ] [ -r fs-revision-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 cor-
responding 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 heuristically 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 deter-
mine the appropriate 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, 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 compatibility. 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 devel-
oping 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.
-I inode-size
Specify the inode size. The default inode-size used by mke2fs is 128. inode-size can be 128, 256, 512 or
1024. This value generally shouldn't be changed!
-j Create the filesystem with an ext3 journal. If the -J option is not specified, the default journal param-
eters 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 filesys-
tem. In addition, while there is support for attaching multiple filesystems to a single
external journal, the Linux kernel and e2fsck(8) do not currently support shared external
journals yet.
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 jour-
nal 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 gener-
ated 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 auto-
matically pass the correct parameters to the badblocks program.
-L new-volume-label
Set the volume label for the filesystem to new-volume-label. The maximum length of the volume label is 16
bytes.
-m reserved-blocks-percentage
Specify the percentage of the filesystem blocks reserved for the super-user. This avoids fragmentation,
and allows root-owned daemons, such as syslogd(8), to continue to function correctly after non-privileged
processes are prevented from writing to the filesystem. The default percentage is 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 filesystem 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 executable.
-O feature[,...]
Create filesystem with given features (filesystem options), overriding the default filesystem options.
The default features which are enabled by default are specified by the base_features relation, either in
the [libdefaults] section in the /etc/mke2fs.conf configuration file, or in the subsection of the
[fs_types] section for the filesystem type as specified by the -T option. The filesystem type-specific
configuration setting found in the [fs_types] section will override the global default found in [libde-
faults].
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 default_features relation for the filesystem type
being created, or in the [libdefaults] 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.
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 regular ext2 filesystem.
Note that external-journal must be created with the same block size as the filesystems that
will be using it.
resize_inode
Reserve space so the block group descriptor table may grow in the future. Useful for online
resizing using resize2fs. By default mke2fs will attempt to reserve enough space so that the
filesystem may grow to 1024 times its initial size. This can be changed using resize extended
option.
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 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.
-T fs-type
Specify how the filesystem is going to be used, so that mke2fs can choose optimal filesystem parameters
for that use. The filesystem types that are can be supported are defined in the configuration file
/etc/mke2fs.conf(5). The default configuration file contains definitions for the filesystem types: small,
floppy, news, largefile, and largefile4.
-v Verbose execution.
-V Print the version number of mke2fs and exit.
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.sourceforge.net.
RELATED
mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8)
CATEGORY