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mke2fs - create an ext2/ext3 filesystem
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 ]
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.
Specify the size of blocks in bytes. Valid block size vales are
1024, 2048 and 4096 bytes per block. If omitted, mke2fs blocksize
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 certain
hardware devices which require that the blocksize be a multiple
- 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:
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.
- -f fragment-size
Specify the size of fragments in bytes.
- Force mke2fs to create a filesystem, even if the specified
device is not a partition on a block special device, or if other
parameters do not make sense. In order to force mke2fs to create
a filesystem even if the filesystem appears to be in use or
is mounted (a truly dangerous thing to do), this option must be
- -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.
- -I inode-size
Specify the size of each inode in bytes. mke2fs creates
128-byte inodes by default. In kernels after 2.6.10 and some
earlier vendor kernels it is possible to utilize larger inodes
to store extended attributes for improved performance. The
inode-size value must be a power of two larger or equal to 128.
The larger the inode-size the more space the inode table will
consume, and this reduces the usable space in the filesystem and
can also negatively impact performance. Using the default value
is always safe, though it may be desirable to use 256-byte
inodes if full backward compatibility is not a concern.
Extended attributes stored in large inodes are not visible with
older kernels, and such filesystems will not be mountable with
2.4 kernels at all. It is not possible to change this value
after the filesystem is created.
- 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 commandline.
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. 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, 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.
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
- -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 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%.
- 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
- 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 [libdefaults].
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
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.
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.
Create a filesystem with fewer superblock backup
copies (saves space on large filesystems).
- 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.
- 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.
- Verbose execution.
- 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 second
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
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