mke2fs - create an ext2/ext3 filesystem
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-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 ]
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 speci-
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 determine
the appropriate block size, with the constraint that the block
size will be at least block-size bytes. This is useful for cer-
tain hardware devices which require that the blocksize be a mul-
tiple 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.
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:
Configure the filesystem for a RAID array with
stripe-size 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.
-F Force mke2fs 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 gener-
ally 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.
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 cor-
rect 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.
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 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
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, exter-
nal-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
Only one of the size or device options can be given for a
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 auto-
matically pass the correct parameters to the badblocks program.
-L Set the volume label for the filesystem.
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
-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!)
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.
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.
Create filesystem with given features (filesystem options),
overriding the default filesystem options. 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 cre-
ator-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 fea-
tures, even if mke2fs is run on a system which can support them.
The following filesystem options are supported:
Use hashed b-trees to speed up lookups in large
Store file type information in directory entries.
Create an ext3 journal (as if using the -j option).
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.
Create a filesystem with fewer superblock backup
copies (saves space on large filesystems).
-q Quiet execution. Useful if mke2fs 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.
-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 salvage-
able. It is critical to specify the correct filesystem block-
size when using this option, or there is no chance of recovery.
Specify how the filesystem is going to be used, so that mke2fs
can chose optimal filesystem parameters for that use. The sup-
ported 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.
This version of mke2fs has been written by Theodore Ts’o
mke2fs accepts the -f option but currently ignores it because the sec-
ond extended file system does not support fragments yet.
There may be other ones. Please, report them to the author.
mke2fs is part of the e2fsprogs package and is available from
badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8)
E2fsprogs version 1.38 June 2005 MKE2FS(8)
Man(1) output converted with