Linux "mke2fs" Command Line Options and Examples
create an ext2/ext3/ext4 filesystem

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.


Usage:

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 ]






Command Line Options:

-b
Specify the size of blocks in bytes. Valid block-size values are 1024, 2048 and 4096 bytes per block. If omitted, block-sizeis 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 theconstraint that the block size will be at least block-size bytes. This is useful for certain hardware devices which requirethat the blocksize be a multiple of 2k.
mke2fs -b ...
-C
Specify the size of cluster in bytes for filesystems using the bigalloc feature. Valid cluster-size values are from 2048 to256M bytes per cluster. This can only be specified if the bigalloc feature is enabled. (See the ext4 (5) man page for moredetails about bigalloc.) The default cluster size if bigalloc is enabled is 16 times the block size.
mke2fs -C ...
-d
Copy the contents of the given directory into the root directory of the filesystem.
mke2fs -d ...
-e
Change the behavior of the kernel code when errors are detected. In all cases, a filesystem error will cause e2fsck(8) tocheck 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.
mke2fs -e ...
-E
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 compat‐ibility, but is deprecated. The following extended options are supported:mmp_update_interval=intervalAdjust the initial MMP update interval to interval seconds. Specifying an interval of 0 means to use the defaultinterval. The specified interval must be less than 300 seconds. Requires that the mmp feature be enabled.stride=stride-sizeConfigure the filesystem for a RAID array with stride-size filesystem blocks. This is the number of blocks read orwritten to disk before moving to the next disk, which is sometimes referred to as the chunk size. This mostlyaffects placement of filesystem metadata like bitmaps at mke2fs time to avoid placing them on a single disk, whichcan hurt performance. It may also be used by the block allocator.stripe_width=stripe-widthConfigure the filesystem for a RAID array with stripe-width filesystem blocks per stripe. This is typicallystride-size * N, where N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one paritydisk, 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=offsetCreate the filesystem at an offset from the beginning of the device or file. This can be useful when creatingdisk images for virtual machines.resize=max-online-resizeReserve 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. Thisspeeds up filesystem initialization noticeably, but it requires the kernel to finish initializing the filesystemin the background when the filesystem is first mounted. If the option value is omitted, it defaults to 1 toenable 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 initializationnoticeably, but carries some small risk if the system crashes before the journal has been overwritten entirely onetime. 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 backupsuperblocks 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 theflex_bg file system feature to be enabled in order for it to have effect, and will also create the journal at thebeginning of the file system. This option is useful for flash devices that use SLC flash at the beginning of thedisk. It also maximizes the range of contiguous data blocks, which can be useful for certain specialized usecases, 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 groupID of the user running mke2fs. In mke2fs 1.42 and earlier the UID and GID of the root directory were set bydefault to the UID and GID of the user running the mke2fs command. The root_owner= option allows explicitly spec‐ifying these values, and avoid side-effects for users that do not expect the contents of the filesystem to changebased on the user running mke2fs.test_fsSet a flag in the filesystem superblock indicating that it may be mounted using experimental kernel code, such asthe ext4dev filesystem.discardAttempt 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 thediscard and before write returns zero), then mark all not-yet-zeroed inode tables as zeroed. This significantlyspeeds up filesystem initialization. This is set as default.nodiscardDo not attempt to discard blocks at mkfs time.quotatypeSpecify 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 quotafeature is set. The default quota types to be initialized if this option is not specified is both user and groupquotas. If the project feature is enabled that project quotas will be initialized as well.
mke2fs -E ...
-g
Specify the number of blocks in a block group. There is generally no reason for the user to ever set this parameter, as thedefault is optimal for the filesystem. (For administrators who are creating filesystems on RAID arrays, it is preferable touse the stride RAID parameter as part of the -E option rather than manipulating the number of blocks per group.) This optionis 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.
mke2fs -g ...
-G
Specify the number of block groups that will be packed together to create a larger virtual block group (or "flex_bg group") inan ext4 filesystem. This improves meta-data locality and performance on meta-data heavy workloads. The number of groups mustbe a power of 2 and may only be specified if the flex_bg filesystem feature is enabled.
mke2fs -G ...
-i
Specify the bytes/inode ratio. mke2fs creates an inode for every bytes-per-inode bytes of space on the disk. The larger thebytes-per-inode ratio, the fewer inodes will be created. This value generally shouldn't be smaller than the blocksize of thefilesystem, since in that case more inodes would be made than can ever be used. Be warned that it is not possible to changethis ratio on a filesystem after it is created, so be careful deciding the correct value for this parameter. Note that resiz‐ing a filesystem changes the number of inodes to maintain this ratio.
mke2fs -i ...
-I
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 theinode-size the more space the inode table will consume, and this reduces the usable space in the filesystem and can also nega‐tively 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 storeextended 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 defaultinode size is 256 bytes for most file systems, except for small file systems where the inode size will be 128 bytes.
mke2fs -I ...
-J
Create the ext3 journal using options specified on the command-line. Journal options are comma separated, and may take anargument using the equals ('=') sign. The following journal options are supported:size=journal-sizeCreate an internal journal (i.e., stored inside the filesystem) of size journal-size megabytes. The size of thejournal must be at least 1024 filesystem blocks (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.) andmay be no more than 10,240,000 filesystem blocks or half the total file system size (whichever is smaller)location=journal-locationSpecify the location of the journal. The argument journal-location can either be specified as a block number, orif the number has a units suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the beginning of the filesystem.device=external-journalAttach the filesystem to the journal block device located on external-journal. The external journal must alreadyhave been created using the commandmke2fs -O journal_dev external-journalNote 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 ande2fsck(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 orUUID=UUID to locate the external journal by either the volume label or UUID stored in the ext2 superblock at thestart of the journal. Use dumpe2fs(8) to display a journal device's volume label and UUID. See also the -Loption of tune2fs(8).Only one of the size or device options can be given for a filesystem.
mke2fs -J ...
-l
Read the bad blocks list from filename. Note that the block numbers in the bad block list must be generated using the sameblock size as used by mke2fs. As a result, the -c option to mke2fs is a much simpler and less error-prone method of checkinga disk for bad blocks before formatting it, as mke2fs will automatically pass the correct parameters to the badblocks program.
mke2fs -l ...
-L
Set the volume label for the filesystem to new-volume-label. The maximum length of the volume label is 16 bytes.
mke2fs -L ...
-m
Specify the percentage of the filesystem blocks reserved for the super-user. This avoids fragmentation, and allows root-owneddaemons, such as syslogd(8), to continue to function correctly after non-privileged processes are prevented from writing tothe filesystem. The default percentage is 5%.
mke2fs -m ...
-M
Set the last mounted directory for the filesystem. This might be useful for the sake of utilities that key off of the lastmounted directory to determine where the filesystem should be mounted.
mke2fs -M ...
-N
Overrides the default calculation of the number of inodes that should be reserved for the filesystem (which is based on thenumber of blocks and the bytes-per-inode ratio). This allows the user to specify the number of desired inodes directly.
mke2fs -N ...
-o
Overrides the default value of the "creator operating system" field of the filesystem. The creator field is set by default tothe name of the OS the mke2fs executable was compiled for.
mke2fs -o ...
-O
Create a filesystem with the given features (filesystem options), overriding the default filesystem options. The featuresthat 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, fur‐ther modified by the features relation found in the [fs_types] subsections for the filesystem and usage types. See themke2fs.conf(5) manual page for more details. The filesystem type-specific configuration setting found in the [fs_types] sec‐tion 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 isnot given, by the default_features relation for the filesystem type being created, or in the [defaults] section of the config‐uration file.The filesystem feature set is comprised of a list of features, separated by commas, that are to be enabled. To disable a fea‐ture, simply prefix the feature name with a caret ('^') character. Features with dependencies will not be removed success‐fully. The pseudo-filesystem feature "none" will clear all filesystem features.For more information about the features which can be set, please seethe manual page ext4(5).
mke2fs -O ...
-q
Quiet execution. Useful if mke2fs is run in a script.
mke2fs -q ...
-r
Set the filesystem revision for the new filesystem. Note that 1.2 kernels only support revision 0 filesystems. The defaultis to create revision 1 filesystems.
mke2fs -r ...
-t
Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is to be created. If this option is not specified, mke2fswill pick a default either via how the command was run (for example, using a name of the form mkfs.ext2, mkfs.ext3, etc.) orvia 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 cre‐ate 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 ext3filesystem code in the Linux kernel.)
mke2fs -t ...
-T
Specify how the filesystem is going to be used, so that mke2fs can choose optimal filesystem parameters for that use. Theusage types that are supported are defined in the configuration file /etc/mke2fs.conf. The user may specify one or more usagetypes 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 becreated. If the filesystem size is less than 3 megabytes, mke2fs will use the filesystem type floppy. If the filesystem sizeis greater than or equal to 3 but less than 512 megabytes, mke2fs(8) will use the filesystem type small. If the filesystemsize is greater than or equal to 4 terabytes but less than 16 terabytes, mke2fs(8) will use the filesystem type big. If thefilesystem 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.
mke2fs -T ...
-U
Set the universally unique identifier (UUID) of the filesystem to UUID. The format of the UUID is a series of hex digits sep‐arated by hyphens, like this: "c1b9d5a2-f162-11cf-9ece-0020afc76f16". The UUID parameter may also be one of the following:clear clear the filesystem UUIDrandom generate a new randomly-generated UUIDtime generate a new time-based UUID
mke2fs -U ...
-v
Verbose execution.
mke2fs -v ...
-V
Print the version number of mke2fs and exit.
mke2fs -V ...
-z
Before overwriting a file system block, write the old contents of the block to an undo file. This undo file can be used withe2undo(8) to restore the old contents of the file system should something go wrong. If the empty string is passed as theundo_file argument, the undo file will be written to a file named mke2fs-device.e2undo in the directory specified via theE2FSPROGS_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.ENVIRONMENTMKE2FS_SYNCIf set to non-zero integer value, its value is used to determine how often sync(2) is called during inode table initializa‐tion.MKE2FS_CONFIGDetermines the location of the configuration file (see mke2fs.conf(5)).MKE2FS_FIRST_META_BGIf set to non-zero integer value, its value is used to determine first meta block group. This is mostly for debugging pur‐poses.MKE2FS_DEVICE_SECTSIZEIf set to non-zero integer value, its value is used to determine logical sector size of the device.MKE2FS_DEVICE_PHYS_SECTSIZEIf set to non-zero integer value, its value is used to determine physical sector size of the device.MKE2FS_SKIP_CHECK_MSGIf set, do not show the message of filesystem automatic check caused by mount count or check interval.AUTHORThis version of mke2fs has been written by Theodore Ts'o <tytso@mit.edu>.AVAILABILITYmke2fs is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net.
mke2fs -z ...