Ubuntu Manpage: mke2fs - create an ext2/ext3/ext4 file system

Provided by: e2fsprogs_1.47.0-1ubuntu1_amd64

NAME

       mke2fs - create an ext2/ext3/ext4 file system

SYNOPSIS

       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 ]

DESCRIPTION

       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.

OPTIONS

-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, mke2fs(8)
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, mke2fs(8) will use the file system
type big. If the file system size is greater than or equal to 16 terabytes,
mke2fs(8) will use the file system type huge. Otherwise, mke2fs(8) 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.

ENVIRONMENT

       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.

AUTHOR

       This version of mke2fs has been written by Theodore Ts'o <tytso@mit.edu>.

AVAILABILITY

       mke2fs   is    part    of    the    e2fsprogs    package    and    is    available    from
       http://e2fsprogs.sourceforge.net.