2 .\" Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved.
3 .\" This file may be copied under the terms of the GNU Public License.
5 .TH MKE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
7 mke2fs \- create an ext2/ext3/ext4 filesystem
63 .I reserved-blocks-percentage
71 [^]\fIfeature\fR[,...]
96 .I last-mounted-directory
129 @JDEV@.B "mke2fs \-O journal_dev"
134 .\" No external-journal specific journal options yet (size is ignored)
137 .\" @JDEV@.I journal-options
141 @JDEV@.I volume-label
152 @JDEV@.I external-journal
158 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
159 partition (or file) named by
162 The file system size is specified by
166 does not have a suffix, it is interpreted as power-of-two kilobytes,
170 option is specified, in which case
172 is interpreted as the number of
174 blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't'
175 (either upper-case or lower-case), then it is interpreted in
176 power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
181 will create the file system based on the device size.
197 will create a file system for use with ext3,
199 will create a file system for use with ext4, and so on.
201 The defaults of the parameters for the newly created filesystem, if not
202 overridden by the options listed below, are controlled by the
204 configuration file. See the
206 manual page for more details.
209 .BI \-b " block-size"
210 Specify the size of blocks in bytes. Valid block-size values are powers of two
211 from 1024 up to 65536 (however note that the kernel is able to mount only
212 filesystems with block-size smaller or equal to the system page size - 4k on
213 x86 systems, upto 64k on ppc64 or aarch64 depending on kernel configuration).
214 If omitted, block-size is heuristically determined by the filesystem size and
215 the expected usage of the filesystem (see the
217 option). In most common cases, the default block size is 4k. If
219 is preceded by a negative sign ('-'), then
221 will use heuristics to determine the
222 appropriate block size, with the constraint that the block size will be
225 bytes. This is useful for certain hardware devices which require that
226 the blocksize be a multiple of 2k.
229 Check the device for bad blocks before creating the file system. If
230 this option is specified twice, then a slower read-write
231 test is used instead of a fast read-only test.
233 .B \-C " cluster-size"
234 Specify the size of cluster in bytes for filesystems using the bigalloc
235 feature. Valid cluster-size values are from 2048 to 256M bytes per
236 cluster. This can only be specified if the bigalloc feature is
239 man page for more details about bigalloc.) The default cluster size if
240 bigalloc is enabled is 16 times the block size.
242 .BI \-d " root-directory"
243 Copy the contents of the given directory into the root directory of the
247 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
248 lot of buffer cache memory, which may impact other applications running
249 on a busy server. This option will cause mke2fs to run much more
250 slowly, however, so there is a tradeoff to using direct I/O.
252 .BI \-e " error-behavior"
253 Change the behavior of the kernel code when errors are detected.
254 In all cases, a filesystem error will cause
256 to check the filesystem on the next boot.
258 can be one of the following:
262 Continue normal execution.
265 Remount filesystem read-only.
268 Cause a kernel panic.
271 .BI \-E " extended-options"
272 Set extended options for the filesystem. Extended options are comma
273 separated, and may take an argument using the equals ('=') sign. The
277 in earlier versions of
281 option is still accepted for backwards compatibility, but is deprecated.
282 The following extended options are supported:
285 .BI encoding= encoding-name
288 feature in the super block and set
290 as the encoding to be used. If
292 is not specified, the encoding defined in
296 .BI encoding_flags= encoding-flags
297 Define parameters for file name character encoding operations. If a
298 flag is not changed using this parameter, its default value is used.
300 should be a comma-separated lists of flags to be enabled. To disable a
301 flag, add it to the list with the prefix "no".
303 The only flag that can be set right now is
305 which means that invalid strings should be rejected by the file system.
306 In the default configuration, the
310 .BI mmp_update_interval= interval
311 Adjust the initial MMP update interval to
313 seconds. Specifying an
315 of 0 means to use the default interval. The specified interval must
316 be less than 300 seconds. Requires that the
320 .BI stride= stride-size
321 Configure the filesystem for a RAID array with
323 filesystem blocks. This is the number of blocks read or written to disk
324 before moving to the next disk, which is sometimes referred to as the
326 This mostly affects placement of filesystem metadata like bitmaps at
328 time to avoid placing them on a single disk, which can hurt performance.
329 It may also be used by the block allocator.
331 .BI stripe_width= stripe-width
332 Configure the filesystem for a RAID array with
334 filesystem blocks per stripe. This is typically stride-size * N, where
335 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
336 parity disk, so N will be the number of disks in the array minus 1).
337 This allows the block allocator to prevent read-modify-write of the
338 parity in a RAID stripe if possible when the data is written.
341 Create the filesystem at an offset from the beginning of the device or
342 file. This can be useful when creating disk images for virtual machines.
344 .BI resize= max-online-resize
345 Reserve enough space so that the block group descriptor table can grow
346 to support a filesystem that has
350 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
351 If enabled and the uninit_bg feature is enabled, the inode table will
352 not be fully initialized by
354 This speeds up filesystem
355 initialization noticeably, but it requires the kernel to finish
356 initializing the filesystem in the background when the filesystem is
357 first mounted. If the option value is omitted, it defaults to 1 to
358 enable lazy inode table zeroing.
360 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
361 If enabled, the journal inode will not be fully zeroed out by
363 This speeds up filesystem initialization noticeably, but carries some
364 small risk if the system crashes before the journal has been overwritten
365 entirely one time. If the option value is omitted, it defaults to 1 to
366 enable lazy journal inode zeroing.
371 will copy the extended attributes of the files in the directory
372 hierarchy specified via the (optional)
374 option. This will disable the copy and leaves the files in the newly
375 created file system without any extended attributes.
377 .BI num_backup_sb= <0|1|2>
380 file system feature is enabled this option controls whether there will
381 be 0, 1, or 2 backup superblocks created in the file system.
383 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
384 Place the allocation bitmaps and the inode table at the beginning of the
385 disk. This option requires that the flex_bg file system feature to be
386 enabled in order for it to have effect, and will also create the journal
387 at the beginning of the file system. This option is useful for flash
388 devices that use SLC flash at the beginning of the disk.
389 It also maximizes the range of contiguous data blocks, which
390 can be useful for certain specialized use cases, such as supported
393 .BI root_owner [=uid:gid]
394 Specify the numeric user and group ID of the root directory. If no UID:GID
395 is specified, use the user and group ID of the user running \fBmke2fs\fR.
396 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
397 set by default to the UID and GID of the user running the mke2fs command.
398 The \fBroot_owner=\fR option allows explicitly specifying these values,
399 and avoid side-effects for users that do not expect the contents of the
400 filesystem to change based on the user running \fBmke2fs\fR.
403 Set a flag in the filesystem superblock indicating that it may be
404 mounted using experimental kernel code, such as the ext4dev filesystem.
407 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
408 on solid state devices and sparse / thin-provisioned storage). When the device
409 advertises that discard also zeroes data (any subsequent read after the discard
410 and before write returns zero), then mark all not-yet-zeroed inode tables as
411 zeroed. This significantly speeds up filesystem initialization. This is set
415 Do not attempt to discard blocks at mkfs time.
418 Specify the which quota types (usrquota, grpquota, prjquota) which
419 should be enabled in the created file system. The argument of this
420 extended option should be a colon separated list. This option has
423 feature is set. The default quota types to be initialized if this
424 option is not specified is both user and group quotas. If the project
425 feature is enabled that project quotas will be initialized as well.
431 to create a filesystem, even if the specified device is not a partition
432 on a block special device, or if other parameters do not make sense.
435 to create a filesystem even if the filesystem appears to be in use
436 or is mounted (a truly dangerous thing to do), this option must be
439 .BI \-g " blocks-per-group"
440 Specify the number of blocks in a block group. There is generally no
441 reason for the user to ever set this parameter, as the default is optimal
442 for the filesystem. (For administrators who are creating
443 filesystems on RAID arrays, it is preferable to use the
445 RAID parameter as part of the
447 option rather than manipulating the number of blocks per group.)
448 This option is generally used by developers who
449 are developing test cases.
451 If the bigalloc feature is enabled, the
453 option will specify the number of clusters in a block group.
455 .BI \-G " number-of-groups"
456 Specify the number of block groups that will be packed together to
457 create a larger virtual block group (or "flex_bg group") in an
458 ext4 filesystem. This improves meta-data locality and performance
459 on meta-data heavy workloads. The number of groups must be a power
460 of 2 and may only be specified if the
462 filesystem feature is enabled.
464 .BI \-i " bytes-per-inode"
465 Specify the bytes/inode ratio.
467 creates an inode for every
469 bytes of space on the disk. The larger the
471 ratio, the fewer inodes will be created. This value generally shouldn't
472 be smaller than the blocksize of the filesystem, since in that case more
473 inodes would be made than can ever be used. Be warned that it is not
474 possible to change this ratio on a filesystem after it is created, so be
475 careful deciding the correct value for this parameter. Note that resizing
476 a filesystem changes the number of inodes to maintain this ratio.
478 .BI \-I " inode-size"
479 Specify the size of each inode in bytes.
482 value must be a power of 2 larger or equal to 128. The larger the
484 the more space the inode table will consume, and this reduces the usable
485 space in the filesystem and can also negatively impact performance.
487 possible to change this value after the filesystem is created.
489 File systems with an inode size of 128 bytes do not support timestamps
490 beyond January 19, 2038. Inodes which are 256 bytes or larger will
491 support extended timestamps, project id's, and the ability to store some
492 extended attributes in the inode table for improved performance.
494 The default inode size is controlled by the
498 file shipped with e2fsprogs, the default inode size is 256 bytes for
499 most file systems, except for small file systems where the inode size
503 Create the filesystem with an ext3 journal. If the
505 option is not specified, the default journal parameters will be used to
506 create an appropriately sized journal (given the size of the filesystem)
507 stored within the filesystem. Note that you must be using a kernel
508 which has ext3 support in order to actually make use of the journal.
510 .BI \-J " journal-options"
511 Create the ext3 journal using options specified on the command-line.
512 Journal options are comma
513 separated, and may take an argument using the equals ('=') sign.
514 The following journal options are supported:
517 .BI size= journal-size
518 Create an internal journal (i.e., stored inside the filesystem) of size
521 The size of the journal must be at least 1024 filesystem blocks
522 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
523 and may be no more than 10,240,000 filesystem blocks or half the total
524 file system size (whichever is smaller)
526 .BI location =journal-location
527 Specify the location of the journal. The argument
529 can either be specified as a block number, or if the number has a units
530 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
531 beginning of the file system.
533 @JDEV@.BI device= external-journal
534 @JDEV@Attach the filesystem to the journal block device located on
535 @JDEV@.IR external-journal .
537 @JDEV@journal must already have been created using the command
539 @JDEV@.B mke2fs -O journal_dev
540 @JDEV@.I external-journal
543 @JDEV@.I external-journal
544 @JDEV@must have been created with the
545 @JDEV@same block size as the new filesystem.
546 @JDEV@In addition, while there is support for attaching
547 @JDEV@multiple filesystems to a single external journal,
548 @JDEV@the Linux kernel and
550 @JDEV@do not currently support shared external journals yet.
552 @JDEV@Instead of specifying a device name directly,
553 @JDEV@.I external-journal
554 @JDEV@can also be specified by either
555 @JDEV@.BI LABEL= label
558 @JDEV@to locate the external journal by either the volume label or UUID
559 @JDEV@stored in the ext2 superblock at the start of the journal. Use
560 @JDEV@.BR dumpe2fs (8)
561 @JDEV@to display a journal device's volume label and UUID. See also the
564 @JDEV@.BR tune2fs (8).
567 @JDEV@Only one of the
568 @JDEV@.BR size " or " device
569 @JDEV@options can be given for a filesystem.
572 Read the bad blocks list from
574 Note that the block numbers in the bad block list must be generated
575 using the same block size as used by
581 is a much simpler and less error-prone method of checking a disk for bad
582 blocks before formatting it, as
584 will automatically pass the correct parameters to the
588 .BI \-L " new-volume-label"
589 Set the volume label for the filesystem to
590 .IR new-volume-label .
591 The maximum length of the
592 volume label is 16 bytes.
594 .BI \-m " reserved-blocks-percentage"
595 Specify the percentage of the filesystem blocks reserved for
596 the super-user. This avoids fragmentation, and allows root-owned
599 to continue to function correctly after non-privileged processes are
600 prevented from writing to the filesystem. The default percentage
603 .BI \-M " last-mounted-directory"
604 Set the last mounted directory for the filesystem. This might be useful
605 for the sake of utilities that key off of the last mounted directory to
606 determine where the filesystem should be mounted.
611 to not actually create a filesystem, but display what it
612 would do if it were to create a filesystem. This can be used to
613 determine the location of the backup superblocks for a particular
614 filesystem, so long as the
616 parameters that were passed when the
617 filesystem was originally created are used again. (With the
619 option added, of course!)
621 .BI \-N " number-of-inodes"
622 Overrides the default calculation of the number of inodes that should be
623 reserved for the filesystem (which is based on the number of blocks and
626 ratio). This allows the user to specify the number
627 of desired inodes directly.
629 .BI \-o " creator-os"
630 Overrides the default value of the "creator operating system" field of the
631 filesystem. The creator field is set by default to the name of the OS the
633 executable was compiled for.
635 .B "\-O \fR[^]\fIfeature\fR[,...]"
636 Create a filesystem with the given features (filesystem options),
637 overriding the default filesystem options. The features that are
638 enabled by default are specified by the
640 relation, either in the
647 subsections for the usage types as specified by the
649 option, further modified by the
651 relation found in the
653 subsections for the filesystem and usage types. See the
655 manual page for more details.
656 The filesystem type-specific configuration setting found in the
658 section will override the global default found in
661 The filesystem feature set will be further edited
662 using either the feature set specified by this option,
663 or if this option is not given, by the
665 relation for the filesystem type being created, or in the
667 section of the configuration file.
669 The filesystem feature set is comprised of a list of features, separated
670 by commas, that are to be enabled. To disable a feature, simply
671 prefix the feature name with a caret ('^') character.
672 Features with dependencies will not be removed successfully.
673 The pseudo-filesystem feature "none" will clear all filesystem features.
675 For more information about the features which can be set, please see
680 Quiet execution. Useful if
685 Set the filesystem revision for the new filesystem. Note that 1.2
686 kernels only support revision 0 filesystems. The default is to
687 create revision 1 filesystems.
690 Write superblock and group descriptors only. This is an extreme
691 measure to be taken only in the very unlikely case that all of
692 the superblock and backup superblocks are corrupted, and a last-ditch
693 recovery method is desired by experienced users. It causes
695 to reinitialize the superblock and group descriptors, while not
696 touching the inode table and the block and inode bitmaps. The
698 program should be run immediately after this option is used, and there
699 is no guarantee that any data will be salvageable. Due to the wide
700 variety of possible options to
702 that affect the on-disk layout, it is critical to specify exactly
703 the same format options, such as blocksize, fs-type, feature flags, and
704 other tunables when using this option, or the filesystem will be further
705 corrupted. In some cases, such as filesystems that have been resized,
706 or have had features enabled after format time, it is impossible to
707 overwrite all of the superblocks correctly, and at least some filesystem
708 corruption will occur. It is best to run this on a full copy of the
709 filesystem so other options can be tried if this doesn't work.
712 .\" Check the device for bad blocks before creating the file system
713 .\" using the specified test.
716 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
718 If this option is not specified,
720 will pick a default either via how
721 the command was run (for example, using a name of the form mkfs.ext2,
722 mkfs.ext3, etc.) or via a default as defined by the
724 file. This option controls which filesystem options are used by
725 default, based on the
727 configuration stanza in
728 .BR /etc/mke2fs.conf .
732 option is used to explicitly add or remove filesystem options that
733 should be set in the newly created filesystem, the
734 resulting filesystem may not be supported by the requested
736 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
737 filesystem that is not supported by the ext3 implementation as found in
738 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
739 will create a filesystem that does not have a journal and hence will not
740 be supported by the ext3 filesystem code in the Linux kernel.)
742 .BI \-T " usage-type[,...]"
743 Specify how the filesystem is going to be used, so that
745 can choose optimal filesystem parameters for that use. The usage
746 types that are supported are defined in the configuration file
747 .BR /etc/mke2fs.conf .
748 The user may specify one or more usage types
749 using a comma separated list.
751 If this option is is not specified,
753 will pick a single default usage type based on the size of the filesystem to
754 be created. If the filesystem size is less than 3 megabytes,
756 will use the filesystem type
758 If the filesystem size is greater than or equal to 3 but less than
761 will use the filesystem type
763 If the filesystem size is greater than or equal to 4 terabytes but less than
766 will use the filesystem type
768 If the filesystem size is greater than or equal to 16 terabytes,
770 will use the filesystem type
774 will use the default filesystem type
778 Set the universally unique identifier (UUID) of the filesystem to
780 The format of the UUID is a series of hex digits separated by hyphens,
782 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
785 parameter may also be one of the following:
789 clear the filesystem UUID
792 generate a new randomly-generated UUID
795 generate a new time-based UUID
802 Print the version number of
807 Before overwriting a file system block, write the old contents of the block to
808 an undo file. This undo file can be used with e2undo(8) to restore the old
809 contents of the file system should something go wrong. If the empty string is
810 passed as the undo_file argument, the undo file will be written to a file named
811 mke2fs-\fIdevice\fR.e2undo in the directory specified via the
812 \fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
813 in the configuration file.
815 WARNING: The undo file cannot be used to recover from a power or system crash.
819 If set to non-zero integer value, its value is used to determine how often
821 is called during inode table initialization.
824 Determines the location of the configuration file (see
825 .BR mke2fs.conf (5)).
827 .B MKE2FS_FIRST_META_BG
828 If set to non-zero integer value, its value is used to determine first meta
829 block group. This is mostly for debugging purposes.
831 .B MKE2FS_DEVICE_SECTSIZE
832 If set to non-zero integer value, its value is used to determine logical
836 .B MKE2FS_DEVICE_PHYS_SECTSIZE
837 If set to non-zero integer value, its value is used to determine physical
841 .B MKE2FS_SKIP_CHECK_MSG
842 If set, do not show the message of filesystem automatic check caused by
843 mount count or check interval.
847 has been written by Theodore Ts'o <tytso@mit.edu>.
850 is part of the e2fsprogs package and is available from
851 http://e2fsprogs.sourceforge.net.