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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | AUTHOR | AVAILABILITY | SEE ALSO | COLOPHON |
MKE2FS(8) System Manager's Manual MKE2FS(8)
mke2fs - create an ext2/ext3/ext4 filesystem
mke2fs [ -c | -l filename ] [ -b block-size ] [ -d root-directory ] [
-D ] [ -g blocks-per-group ] [ -G number-of-groups ] [ -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 fs-type ] [ -T usage-type ] [ -U UUID
] [ -V ] [ -e errors-behavior ] [ -z undo_file ] device [ fs-size ]
mke2fs -O journal_dev [ -b block-size ] [ -L volume-label ] [ -n ] [
-q ] [ -v ] external-journal [ fs-size ]
mke2fs is used to create an ext2, ext3, or ext4 filesystem, usually
in a disk partition (or file) named by device.
The file system size is specified by fs-size. If fs-size does not
have a suffix, it is interpreted as power-of-two kilobytes, unless
the -b blocksize option is specified, in which case fs-size is
interpreted as the number of blocksize blocks. If the fs-size is
suffixed by 'k', 'm', 'g', 't' (either upper-case or lower-case),
then it is interpreted in power-of-two kilobytes, megabytes,
gigabytes, terabytes, etc. If fs-size is omitted, mke2fs will create
the file system based on the device size.
If mke2fs is run as mkfs.XXX (i.e., mkfs.ext2, mkfs.ext3, or
mkfs.ext4) the option -t XXX is implied; so mkfs.ext3 will create a
file system for use with ext3, mkfs.ext4 will create a file system
for use with ext4, and so on.
The defaults of the parameters for the newly created filesystem, if
not overridden by the options listed below, are controlled by the
/etc/mke2fs.conf configuration file. See the mke2fs.conf(5) manual
page for more details.
-b block-size
Specify the size of blocks in bytes. Valid block-size values
are 1024, 2048 and 4096 bytes per block. If omitted, block-
size is heuristically determined by the filesystem size and
the expected usage of the filesystem (see the -T option). If
block-size is preceded by a negative sign ('-'), 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 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.
-C cluster-size
Specify the size of cluster in bytes for filesystems using the
bigalloc feature. Valid cluster-size values are from 2048 to
256M bytes per cluster. This can only be specified if the
bigalloc feature is enabled. (See the ext4(5) man page for
more details about bigalloc.) The default cluster size if
bigalloc is enabled is 16 times the block size.
-d root-directory
Copy the contents of the given directory into the root
directory of the filesystem.
-D Use direct I/O when writing to the disk. This avoids mke2fs
dirtying a lot of buffer cache memory, which may impact other
applications running on a busy server. This option will cause
mke2fs to run much more slowly, however, so there is a
tradeoff to using direct I/O.
-e error-behavior
Change the behavior of the kernel code when errors are
detected. In all cases, a filesystem error will cause
e2fsck(8) to check the filesystem on the next boot. error-
behavior can be one of the following:
continue Continue normal execution.
remount-ro Remount filesystem read-only.
panic Cause a kernel panic.
-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, but is deprecated. The following extended
options are supported:
mmp_update_interval=interval
Adjust the initial MMP update interval to interval
seconds. Specifying an interval of 0 means to use
the default interval. The specified interval must
be less than 300 seconds. Requires that the mmp
feature be enabled.
stride=stride-size
Configure the filesystem for a RAID array with
stride-size filesystem blocks. This is the number
of blocks read or written to disk before moving to
the next disk, which is sometimes referred to as
the chunk size. This mostly affects placement of
filesystem metadata like bitmaps at mke2fs time to
avoid placing them on a single disk, which can
hurt performance. It may also be used by the
block allocator.
stripe_width=stripe-width
Configure the filesystem for a RAID array with
stripe-width filesystem blocks per stripe. This is
typically stride-size * N, where N is the number
of data-bearing disks in the RAID (e.g. for RAID 5
there is one parity disk, so N will be the number
of disks in the array minus 1). This allows the
block allocator to prevent read-modify-write of
the parity in a RAID stripe if possible when the
data is written.
offset=offset
Create the filesystem at an offset from the
beginning of the device or file. This can be
useful when creating disk images for virtual
machines.
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.
lazy_itable_init[= <0 to disable, 1 to enable>]
If enabled and the uninit_bg feature is enabled,
the inode table will not be fully initialized by
mke2fs. This speeds up filesystem initialization
noticeably, but it requires the kernel to finish
initializing the filesystem in the background when
the filesystem is first mounted. If the option
value is omitted, it defaults to 1 to enable lazy
inode table zeroing.
lazy_journal_init[= <0 to disable, 1 to enable>]
If enabled, the journal inode will not be fully
zeroed out by mke2fs. This speeds up filesystem
initialization noticeably, but carries some small
risk if the system crashes before the journal has
been overwritten entirely one time. If the option
value is omitted, it defaults to 1 to enable lazy
journal inode zeroing.
num_backup_sb=<0|1|2>
If the sparse_super2 file system feature is
enabled this option controls whether there will be
0, 1, or 2 backup superblocks created in the file
system.
packed_meta_blocks[= <0 to disable, 1 to enable>]
Place the allocation bitmaps and the inode table
at the beginning of the disk. This option
requires that the flex_bg file system feature to
be enabled in order for it to have effect, and
will also create the journal at the beginning of
the file system. This option is useful for flash
devices that use SLC flash at the beginning of the
disk. It also maximizes the range of contiguous
data blocks, which can be useful for certain
specialized use cases, such as supported Shingled
Drives.
root_owner[=uid:gid]
Specify the numeric user and group ID of the root
directory. If no UID:GID is specified, use the
user and group ID of the user running mke2fs. In
mke2fs 1.42 and earlier the UID and GID of the
root directory were set by default to the UID and
GID of the user running the mke2fs command. The
root_owner= option allows explicitly specifying
these values, and avoid side-effects for users
that do not expect the contents of the filesystem
to change based on the user running mke2fs.
test_fs
Set a flag in the filesystem superblock indicating
that it may be mounted using experimental kernel
code, such as the ext4dev filesystem.
discard
Attempt to discard blocks at mkfs time (discarding
blocks initially is useful on solid state devices
and sparse / thin-provisioned storage). When the
device advertises that discard also zeroes data
(any subsequent read after the discard and before
write returns zero), then mark all not-yet-zeroed
inode tables as zeroed. This significantly speeds
up filesystem initialization. This is set as
default.
nodiscard
Do not attempt to discard blocks at mkfs time.
quotatype
Specify the which quota types (usrquota,
grpquota, prjquota) which should be enabled in the
created file system. The argument of this
extended option should be a colon separated list.
This option has effect only if the quota feature
is set. The default quota types to be
initialized if this option is not specified is
both user and group quotas. If the project
feature is enabled that project quotas will be
initialized as well.
-F 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 specified twice.
-g blocks-per-group
Specify the number of blocks in a block group. There is
generally no reason for 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
-E option rather than manipulating the number of blocks per
group.) This option is generally used by developers who are
developing test cases.
If the bigalloc feature is enabled, the -g option will specify
the number of clusters in a block group.
-G number-of-groups
Specify the number of block groups that will be packed
together to create a larger virtual block group (or "flex_bg
group") in an ext4 filesystem. This improves meta-data
locality and performance on meta-data heavy workloads. The
number of groups must be a power of 2 and may only be
specified if the flex_bg filesystem feature is enabled.
-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 in that case more inodes would be
made than can ever be used. Be warned that it is not possible
to change this ratio on a filesystem after it is created, so
be careful deciding the correct value for this parameter.
Note that resizing a filesystem changes the numer of inodes to
maintain this ratio.
-I inode-size
Specify the size of each inode in bytes. The inode-size value
must be a power of 2 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. It is not possible to change
this value after the filesystem is created.
In kernels after 2.6.10 and some earlier vendor kernels it is
possible to utilize inodes larger than 128 bytes to store
extended attributes for improved performance. 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.
The default inode size is controlled by the mke2fs.conf(5)
file. In the mke2fs.conf file shipped with e2fsprogs, the
default inode size is 256 bytes for most file systems, except
for small file systems where the inode size will be 128 bytes.
-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 10,240,000 filesystem blocks or half the
total file system size (whichever is smaller)
location=journal-location
Specify the location of the journal. The argument
journal-location can either be specified as a
block number, or if the number has a units suffix
(e.g., 'M', 'G', etc.) interpret it as the offset
from the beginning of the file system.
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.
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 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 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 last-mounted-directory
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
Overrides the default value of the "creator operating system"
field of the filesystem. The creator field is set by default
to the name of the OS the mke2fs executable was compiled for.
-O [^]feature[,...]
Create a filesystem with the given features (filesystem
options), overriding the default filesystem options. The
features that are enabled by default are specified by the
base_features relation, either in the [defaults] section in
the /etc/mke2fs.conf configuration file, or in the [fs_types]
subsections for the usage types as specified by the -T option,
further modified by the features relation found in the
[fs_types] subsections for the filesystem and usage types.
See the mke2fs.conf(5) manual page for more details. The
filesystem type-specific configuration setting found in the
[fs_types] section will override the global default found in
[defaults].
The filesystem feature set will be further edited using either
the feature set specified by this option, or if this option is
not given, by the default_features relation for the filesystem
type being created, or in the [defaults] 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. Features with dependencies will not be removed
successfully. The pseudo-filesystem feature "none" will clear
all filesystem features.
For more information about the features which can be set, please see
the manual page ext4(5).
-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 an
extreme measure to be taken only in the very unlikely case
that all of the superblock and backup superblocks are
corrupted, and a last-ditch recovery method is desired by
experienced users. 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. Due to the
wide variety of possible options to mke2fs that affect the on-
disk layout, it is critical to specify exactly the same format
options, such as blocksize, fs-type, feature flags, and other
tunables when using this option, or the filesystem will be
further corrupted. In some cases, such as filesystems that
have been resized, or have had features enabled after format
time, it is impossible to overwrite all of the superblocks
correctly, and at least some filesystem corruption will occur.
It is best to run this on a full copy of the filesystem so
other options can be tried if this doesn't work.
-t fs-type
Specify the filesystem type (i.e., ext2, ext3, ext4, etc.)
that is to be created. If this option is not specified,
mke2fs will pick a default either via how the command was run
(for example, using a name of the form mkfs.ext2, mkfs.ext3,
etc.) or via a default as defined by the /etc/mke2fs.conf
file. This option controls which filesystem options are used
by default, based on the fstypes configuration stanza in
/etc/mke2fs.conf.
If the -O option is used to explicitly add or remove
filesystem options that should be set in the newly created
filesystem, the resulting filesystem may not be supported by
the requested fs-type. (e.g., "mke2fs -t ext3 -O extent
/dev/sdXX" will create a filesystem that is not supported by
the ext3 implementation as found in the Linux kernel; and
"mke2fs -t ext3 -O ^has_journal /dev/hdXX" will create a
filesystem that does not have a journal and hence will not be
supported by the ext3 filesystem code in the Linux kernel.)
-T usage-type[,...]
Specify how the filesystem is going to be used, so that mke2fs
can choose optimal filesystem parameters for that use. The
usage types that are supported are defined in the
configuration file /etc/mke2fs.conf. The user may specify one
or more usage types using a comma separated list.
If this option is is not specified, mke2fs will pick a single
default usage type based on the size of the filesystem to be
created. If the filesystem size is less than 3 megabytes,
mke2fs will use the filesystem type floppy. If the filesystem
size is greater than or equal to 3 but less than 512
megabytes, mke2fs(8) will use the filesystem type small. If
the filesystem size is greater than or equal to 4 terabytes
but less than 16 terabytes, mke2fs(8) will use the filesystem
type big. If the filesystem size is greater than or equal to
16 terabytes, mke2fs(8) will use the filesystem type huge.
Otherwise, mke2fs(8) will use the default filesystem type
default.
-U UUID
Set the universally unique identifier (UUID) of the filesystem
to UUID. The format of the UUID is a series of hex digits
separated by hyphens, like this:
"c1b9d5a2-f162-11cf-9ece-0020afc76f16". The UUID parameter
may also be one of the following:
clear clear the filesystem UUID
random generate a new randomly-generated UUID
time generate a new time-based UUID
-v Verbose execution.
-V Print the version number of mke2fs and exit.
-z undo_file
Before overwriting a file system block, write the old contents
of the block to an undo file. This undo file can be used with
e2undo(8) to restore the old contents of the file system
should something go wrong. If the empty string is passed as
the undo_file argument, the undo file will be written to a
file named mke2fs-device.e2undo in the directory specified via
the E2FSPROGS_UNDO_DIR environment variable or the undo_dir
directive in the configuration file.
WARNING: The undo file cannot be used to recover from a power
or system crash.
MKE2FS_SYNC
If set to non-zero integer value, its value is used to
determine how often sync(2) is called during inode table
initialization.
MKE2FS_CONFIG
Determines the location of the configuration file (see
mke2fs.conf(5)).
MKE2FS_FIRST_META_BG
If set to non-zero integer value, its value is used to
determine first meta block group. This is mostly for debugging
purposes.
MKE2FS_DEVICE_SECTSIZE
If set to non-zero integer value, its value is used to
determine physical sector size of the device.
MKE2FS_SKIP_CHECK_MSG
If set, do not show the message of filesystem automatic check
caused by mount count or check interval.
This version of mke2fs has been written by Theodore Ts'o
<tytso@mit.edu>.
mke2fs is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8),
ext4(5)
This page is part of the e2fsprogs (utilities for ext2/3/4
filesystems) project. Information about the project can be found at
⟨http://e2fsprogs.sourceforge.net/⟩. It is not known how to report
bugs for this man page; if you know, please send a mail to
man-pages@man7.org. This page was obtained from the project's
upstream Git repository
⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on 2017-07-05.
If you discover any rendering problems in this HTML version of the
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send a mail to man-pages@man7.org
E2fsprogs version 1.43.5-WIP February 2017 MKE2FS(8)
Pages that refer to this page: ext4(5), mke2fs.conf(5), badblocks(8), debugfs(8), dumpe2fs(8), e2fsck(8), e2label(8), e2undo(8), e4crypt(8), e4defrag(8), mke2fs(8), mkfs(8), mklost+found(8), mount(8), resize2fs(8), tune2fs(8)