mke2fs - create an ext2/ext3/ext4 file system
mke2fs [
-c |
-l filename ] [
-b
block-size ] [
-C cluster-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 file system, 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 file system, 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 powers of two from 1024 up to 65536 (however note that the
kernel is able to mount only file systems with block-size smaller or equal
to the system page size - 4k on x86 systems, up to 64k on ppc64 or aarch64
depending on kernel configuration). If omitted, block-size is
heuristically determined by the file system size and the expected usage of
the file system (see the -T option). In most common cases, the
default block size is 4k. 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 file systems 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 file system.
- -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 file system error will cause e2fsck(8) to
check the file system on the next boot. error-behavior can be one
of the following:
- continue
- Continue normal execution.
- remount-ro
- Remount file system read-only.
- panic
- Cause a kernel panic.
-
-E extended-options
- Set extended options for the file system. 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:
-
encoding=encoding-name
- Enable the casefold feature in the super block and
set encoding-name as the encoding to be used. If
encoding-name is not specified, the encoding defined in
mke2fs.conf(5) is used.
-
encoding_flags=encoding-flags
- Define parameters for file name character encoding
operations. If a flag is not changed using this parameter, its default
value is used. encoding-flags should be a comma-separated lists of
flags to be enabled. To disable a flag, add it to the list with the prefix
"no".
The only flag that can be set right now is strict which means that
invalid strings should be rejected by the file system. In the default
configuration, the strict flag is disabled.
-
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 file system for a RAID array with
stride-size file system 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
file system 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 file system for a RAID array with
stripe-width file system 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 file system 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 file system 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 file
system initialization noticeably, but it requires the kernel to finish
initializing the file system in the background when the file system 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 file system 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.
- assume_storage_prezeroed[= <0 to disable, 1
to enable>]
- If enabled, mke2fs assumes that the storage device
has been prezeroed, skips zeroing the journal and inode tables, and
annotates the block group flags to signal that the inode table has been
zeroed.
- no_copy_xattrs
- Normally mke2fs will copy the extended attributes of
the files in the directory hierarchy specified via the (optional)
-d option. This will disable the copy and leaves the files in the
newly created file system without any extended attributes.
-
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 file system to change based on the user
running mke2fs.
- test_fs
- Set a flag in the file system superblock indicating that it
may be mounted using experimental kernel code, such as the ext4dev file
system.
-
orphan_file_size=size
- Set size of the file for tracking unlinked but still open
inodes and inodes with truncate in progress. Larger file allows for better
scalability, reserving a few blocks per cpu is ideal.
- 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 file system 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 file system, 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
file system even if the file system 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 file system. (For administrators who are
creating file systems 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 file system. 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 file system
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 file
system, 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 file
system after it is created, so be careful deciding the correct value for
this parameter. Note that resizing a file system changes the number 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 file system and can also
negatively impact performance. It is not possible to change this value
after the file system is created.
- File systems with an inode size of 128 bytes do not support
timestamps beyond January 19, 2038. Inodes which are 256 bytes or larger
will support extended timestamps, project id's, and the ability to store
some extended attributes in the inode table for improved performance.
- 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 file system 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 file
system) stored within the file system. 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 file
system) of size journal-size megabytes. The size of the journal
must be at least 1024 file system blocks (i.e., 1MB if using 1k blocks,
4MB if using 4k blocks, etc.) and may be no more than 10,240,000 file
system blocks or half the total file system size (whichever is
smaller)
-
fast_commit_size=fast-commit-size
- Create an additional fast commit journal area of size
fast-commit-size kilobytes. This option is only valid if
fast_commit feature is enabled on the file system. If this option
is not specified and if fast_commit feature is turned on, fast
commit area size defaults to journal-size / 64 megabytes. The total
size of the journal with fast_commit feature set is
journal-size + ( fast-commit-size * 1024) megabytes. The
total journal size may be no more than 10,240,000 file system 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 file system 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 file system. In addition, while there
is support for attaching multiple file systems 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 file system.
-
-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 file system to
new-volume-label. The maximum length of the volume label is 16
bytes.
-
-m reserved-blocks-percentage
- Specify the percentage of the file system 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 file
system. The default percentage is 5%.
-
-M last-mounted-directory
- Set the last mounted directory for the file system. This
might be useful for the sake of utilities that key off of the last mounted
directory to determine where the file system should be mounted.
- -n
- Causes mke2fs to not actually create a file system,
but display what it would do if it were to create a file system. This can
be used to determine the location of the backup superblocks for a
particular file system, so long as the mke2fs parameters that were
passed when the file system 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 file system (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 file system. The creator field is set by default
to the name of the OS the mke2fs executable was compiled for.
- -O [^]feature[,...]
- Create a file system with the given features (file system
options), overriding the default file system 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 file system and usage types. See the mke2fs.conf(5) manual page
for more details. The file system type-specific configuration setting
found in the [fs_types] section will override the global default
found in [defaults].
The file system 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 file system type being created,
or in the [defaults] section of the configuration file.
The file system 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-file system feature
"none" will clear all file system 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 file system revision for the new file system. Note
that 1.2 kernels only support revision 0 file systems. The default is to
create revision 1 file systems.
- -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
file system will be further corrupted. In some cases, such as file systems
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 file system corruption will occur. It is best to run this on a full
copy of the file system so other options can be tried if this doesn't
work.
-
-t fs-type
- Specify the file system 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 file
system 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 file system
options that should be set in the newly created file system, the resulting
file system may not be supported by the requested fs-type. (e.g.,
" mke2fs -t ext3 -O extent /dev/sdXX" will create a file
system 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 file system that does not have a journal
and hence will not be supported by the ext3 file system code in the Linux
kernel.)
-
-T usage-type[,...]
- Specify how the file system is going to be used, so that
mke2fs can choose optimal file system 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 file system to be created. If the file
system size is less than 3 megabytes, mke2fs will use the file
system type floppy. If the file system size is greater than or
equal to 3 but less than 512 megabytes, will use the file
system type small. If the file system size is greater than or equal
to 4 terabytes but less than 16 terabytes, will use the
file system type big. If the file system size is greater than or
equal to 16 terabytes, will use the file system type
huge. Otherwise, will use the default file system
type default.
-
-U UUID
- Set the universally unique identifier (UUID) of the file
system 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 file system 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 logical sector size of the device.
- MKE2FS_DEVICE_PHYS_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 file system automatic
check caused by mount count or check interval.
This version of
mke2fs has been written by Theodore Ts'o
<
[email protected]>.
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)