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 file system
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 file system, 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 file system, 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 file systems with block-size smaller or equal to the system page size - 4k on
213 x86 systems, up to 64k on ppc64 or aarch64 depending on kernel configuration).
214 If omitted, block-size is heuristically determined by the file system size and
215 the expected usage of the file system (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 file systems 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 file system error will cause
256 to check the file system on the next boot.
258 can be one of the following:
262 Continue normal execution.
265 Remount file system read-only.
268 Cause a kernel panic.
271 .BI \-E " extended-options"
272 Set extended options for the file system. 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 file system for a RAID array with
323 file system 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 file system 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 file system for a RAID array with
334 file system 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 file system 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 file system 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 file system
355 initialization noticeably, but it requires the kernel to finish
356 initializing the file system in the background when the file system 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 file system 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.
368 .B assume_storage_prezeroed\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
371 assumes that the storage device has been prezeroed, skips zeroing the journal
372 and inode tables, and annotates the block group flags to signal that the inode
373 table has been zeroed.
378 will copy the extended attributes of the files in the directory
379 hierarchy specified via the (optional)
381 option. This will disable the copy and leaves the files in the newly
382 created file system without any extended attributes.
384 .BI num_backup_sb= <0|1|2>
387 file system feature is enabled this option controls whether there will
388 be 0, 1, or 2 backup superblocks created in the file system.
390 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
391 Place the allocation bitmaps and the inode table at the beginning of the
392 disk. This option requires that the flex_bg file system feature to be
393 enabled in order for it to have effect, and will also create the journal
394 at the beginning of the file system. This option is useful for flash
395 devices that use SLC flash at the beginning of the disk.
396 It also maximizes the range of contiguous data blocks, which
397 can be useful for certain specialized use cases, such as supported
400 .BI root_owner [=uid:gid]
401 Specify the numeric user and group ID of the root directory. If no UID:GID
402 is specified, use the user and group ID of the user running \fBmke2fs\fR.
403 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
404 set by default to the UID and GID of the user running the mke2fs command.
405 The \fBroot_owner=\fR option allows explicitly specifying these values,
406 and avoid side-effects for users that do not expect the contents of the
407 file system to change based on the user running \fBmke2fs\fR.
410 Set a flag in the file system superblock indicating that it may be
411 mounted using experimental kernel code, such as the ext4dev file system.
413 .BI orphan_file_size= size
414 Set size of the file for tracking unlinked but still open inodes and inodes
415 with truncate in progress. Larger file allows for better scalability, reserving
416 a few blocks per cpu is ideal.
419 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
420 on solid state devices and sparse / thin-provisioned storage). When the device
421 advertises that discard also zeroes data (any subsequent read after the discard
422 and before write returns zero), then mark all not-yet-zeroed inode tables as
423 zeroed. This significantly speeds up file system initialization. This is set
427 Do not attempt to discard blocks at mkfs time.
430 Specify the which quota types (usrquota, grpquota, prjquota) which
431 should be enabled in the created file system. The argument of this
432 extended option should be a colon separated list. This option has
435 feature is set. The default quota types to be initialized if this
436 option is not specified is both user and group quotas. If the project
437 feature is enabled that project quotas will be initialized as well.
443 to create a file system, even if the specified device is not a partition
444 on a block special device, or if other parameters do not make sense.
447 to create a file system even if the file system appears to be in use
448 or is mounted (a truly dangerous thing to do), this option must be
451 .BI \-g " blocks-per-group"
452 Specify the number of blocks in a block group. There is generally no
453 reason for the user to ever set this parameter, as the default is optimal
454 for the file system. (For administrators who are creating
455 file systems on RAID arrays, it is preferable to use the
457 RAID parameter as part of the
459 option rather than manipulating the number of blocks per group.)
460 This option is generally used by developers who
461 are developing test cases.
463 If the bigalloc feature is enabled, the
465 option will specify the number of clusters in a block group.
467 .BI \-G " number-of-groups"
468 Specify the number of block groups that will be packed together to
469 create a larger virtual block group (or "flex_bg group") in an
470 ext4 file system. This improves meta-data locality and performance
471 on meta-data heavy workloads. The number of groups must be a power
472 of 2 and may only be specified if the
474 file system feature is enabled.
476 .BI \-i " bytes-per-inode"
477 Specify the bytes/inode ratio.
479 creates an inode for every
481 bytes of space on the disk. The larger the
483 ratio, the fewer inodes will be created. This value generally shouldn't
484 be smaller than the blocksize of the file system, since in that case more
485 inodes would be made than can ever be used. Be warned that it is not
486 possible to change this ratio on a file system after it is created, so be
487 careful deciding the correct value for this parameter. Note that resizing
488 a file system changes the number of inodes to maintain this ratio.
490 .BI \-I " inode-size"
491 Specify the size of each inode in bytes.
494 value must be a power of 2 larger or equal to 128. The larger the
496 the more space the inode table will consume, and this reduces the usable
497 space in the file system and can also negatively impact performance.
499 possible to change this value after the file system is created.
501 File systems with an inode size of 128 bytes do not support timestamps
502 beyond January 19, 2038. Inodes which are 256 bytes or larger will
503 support extended timestamps, project id's, and the ability to store some
504 extended attributes in the inode table for improved performance.
506 The default inode size is controlled by the
510 file shipped with e2fsprogs, the default inode size is 256 bytes for
511 most file systems, except for small file systems where the inode size
515 Create the file system with an ext3 journal. If the
517 option is not specified, the default journal parameters will be used to
518 create an appropriately sized journal (given the size of the file system)
519 stored within the file system. Note that you must be using a kernel
520 which has ext3 support in order to actually make use of the journal.
522 .BI \-J " journal-options"
523 Create the ext3 journal using options specified on the command-line.
524 Journal options are comma
525 separated, and may take an argument using the equals ('=') sign.
526 The following journal options are supported:
529 .BI size= journal-size
530 Create an internal journal (i.e., stored inside the file system) of size
533 The size of the journal must be at least 1024 file system blocks
534 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
535 and may be no more than 10,240,000 file system blocks or half the total
536 file system size (whichever is smaller)
538 .BI fast_commit_size= fast-commit-size
539 Create an additional fast commit journal area of size
542 This option is only valid if
545 on the file system. If this option is not specified and if
547 feature is turned on, fast commit area size defaults to
549 / 64 megabytes. The total size of the journal with
555 * 1024) megabytes. The total journal size may be no more than
556 10,240,000 file system blocks or half the total file system size
557 (whichever is smaller).
559 .BI location =journal-location
560 Specify the location of the journal. The argument
562 can either be specified as a block number, or if the number has a units
563 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
564 beginning of the file system.
566 @JDEV@.BI device= external-journal
567 @JDEV@Attach the file system to the journal block device located on
568 @JDEV@.IR external-journal .
570 @JDEV@journal must already have been created using the command
572 @JDEV@.B mke2fs -O journal_dev
573 @JDEV@.I external-journal
576 @JDEV@.I external-journal
577 @JDEV@must have been created with the
578 @JDEV@same block size as the new file system.
579 @JDEV@In addition, while there is support for attaching
580 @JDEV@multiple file systems to a single external journal,
581 @JDEV@the Linux kernel and
583 @JDEV@do not currently support shared external journals yet.
585 @JDEV@Instead of specifying a device name directly,
586 @JDEV@.I external-journal
587 @JDEV@can also be specified by either
588 @JDEV@.BI LABEL= label
591 @JDEV@to locate the external journal by either the volume label or UUID
592 @JDEV@stored in the ext2 superblock at the start of the journal. Use
593 @JDEV@.BR dumpe2fs (8)
594 @JDEV@to display a journal device's volume label and UUID. See also the
597 @JDEV@.BR tune2fs (8).
600 @JDEV@Only one of the
601 @JDEV@.BR size " or " device
602 @JDEV@options can be given for a file system.
605 Read the bad blocks list from
607 Note that the block numbers in the bad block list must be generated
608 using the same block size as used by
614 is a much simpler and less error-prone method of checking a disk for bad
615 blocks before formatting it, as
617 will automatically pass the correct parameters to the
621 .BI \-L " new-volume-label"
622 Set the volume label for the file system to
623 .IR new-volume-label .
624 The maximum length of the
625 volume label is 16 bytes.
627 .BI \-m " reserved-blocks-percentage"
628 Specify the percentage of the file system blocks reserved for
629 the super-user. This avoids fragmentation, and allows root-owned
632 to continue to function correctly after non-privileged processes are
633 prevented from writing to the file system. The default percentage
636 .BI \-M " last-mounted-directory"
637 Set the last mounted directory for the file system. This might be useful
638 for the sake of utilities that key off of the last mounted directory to
639 determine where the file system should be mounted.
644 to not actually create a file system, but display what it
645 would do if it were to create a file system. This can be used to
646 determine the location of the backup superblocks for a particular
647 file system, so long as the
649 parameters that were passed when the
650 file system was originally created are used again. (With the
652 option added, of course!)
654 .BI \-N " number-of-inodes"
655 Overrides the default calculation of the number of inodes that should be
656 reserved for the file system (which is based on the number of blocks and
659 ratio). This allows the user to specify the number
660 of desired inodes directly.
662 .BI \-o " creator-os"
663 Overrides the default value of the "creator operating system" field of the
664 file system. The creator field is set by default to the name of the OS the
666 executable was compiled for.
668 .B "\-O \fR[^]\fIfeature\fR[,...]"
669 Create a file system with the given features (file system options),
670 overriding the default file system options. The features that are
671 enabled by default are specified by the
673 relation, either in the
680 subsections for the usage types as specified by the
682 option, further modified by the
684 relation found in the
686 subsections for the file system and usage types. See the
688 manual page for more details.
689 The file system type-specific configuration setting found in the
691 section will override the global default found in
694 The file system feature set will be further edited
695 using either the feature set specified by this option,
696 or if this option is not given, by the
698 relation for the file system type being created, or in the
700 section of the configuration file.
702 The file system feature set is comprised of a list of features, separated
703 by commas, that are to be enabled. To disable a feature, simply
704 prefix the feature name with a caret ('^') character.
705 Features with dependencies will not be removed successfully.
706 The pseudo-file system feature "none" will clear all file system features.
708 For more information about the features which can be set, please see
713 Quiet execution. Useful if
718 Set the file system revision for the new file system. Note that 1.2
719 kernels only support revision 0 file systems. The default is to
720 create revision 1 file systems.
723 Write superblock and group descriptors only. This is an extreme
724 measure to be taken only in the very unlikely case that all of
725 the superblock and backup superblocks are corrupted, and a last-ditch
726 recovery method is desired by experienced users. It causes
728 to reinitialize the superblock and group descriptors, while not
729 touching the inode table and the block and inode bitmaps. The
731 program should be run immediately after this option is used, and there
732 is no guarantee that any data will be salvageable. Due to the wide
733 variety of possible options to
735 that affect the on-disk layout, it is critical to specify exactly
736 the same format options, such as blocksize, fs-type, feature flags, and
737 other tunables when using this option, or the file system will be further
738 corrupted. In some cases, such as file systems that have been resized,
739 or have had features enabled after format time, it is impossible to
740 overwrite all of the superblocks correctly, and at least some file system
741 corruption will occur. It is best to run this on a full copy of the
742 file system so other options can be tried if this doesn't work.
745 .\" Check the device for bad blocks before creating the file system
746 .\" using the specified test.
749 Specify the file system type (i.e., ext2, ext3, ext4, etc.) that is
751 If this option is not specified,
753 will pick a default either via how
754 the command was run (for example, using a name of the form mkfs.ext2,
755 mkfs.ext3, etc.) or via a default as defined by the
757 file. This option controls which file system options are used by
758 default, based on the
760 configuration stanza in
761 .BR /etc/mke2fs.conf .
765 option is used to explicitly add or remove file system options that
766 should be set in the newly created file system, the
767 resulting file system may not be supported by the requested
769 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
770 file system that is not supported by the ext3 implementation as found in
771 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
772 will create a file system that does not have a journal and hence will not
773 be supported by the ext3 file system code in the Linux kernel.)
775 .BI \-T " usage-type[,...]"
776 Specify how the file system is going to be used, so that
778 can choose optimal file system parameters for that use. The usage
779 types that are supported are defined in the configuration file
780 .BR /etc/mke2fs.conf .
781 The user may specify one or more usage types
782 using a comma separated list.
784 If this option is is not specified,
786 will pick a single default usage type based on the size of the file system to
787 be created. If the file system size is less than 3 megabytes,
789 will use the file system type
791 If the file system size is greater than or equal to 3 but less than
794 will use the file system type
796 If the file system size is greater than or equal to 4 terabytes but less than
799 will use the file system type
801 If the file system size is greater than or equal to 16 terabytes,
803 will use the file system type
807 will use the default file system type
811 Set the universally unique identifier (UUID) of the file system to
813 The format of the UUID is a series of hex digits separated by hyphens,
815 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
818 parameter may also be one of the following:
822 clear the file system UUID
825 generate a new randomly-generated UUID
828 generate a new time-based UUID
835 Print the version number of
840 Before overwriting a file system block, write the old contents of the block to
841 an undo file. This undo file can be used with e2undo(8) to restore the old
842 contents of the file system should something go wrong. If the empty string is
843 passed as the undo_file argument, the undo file will be written to a file named
844 mke2fs-\fIdevice\fR.e2undo in the directory specified via the
845 \fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
846 in the configuration file.
848 WARNING: The undo file cannot be used to recover from a power or system crash.
852 If set to non-zero integer value, its value is used to determine how often
854 is called during inode table initialization.
857 Determines the location of the configuration file (see
858 .BR mke2fs.conf (5)).
860 .B MKE2FS_FIRST_META_BG
861 If set to non-zero integer value, its value is used to determine first meta
862 block group. This is mostly for debugging purposes.
864 .B MKE2FS_DEVICE_SECTSIZE
865 If set to non-zero integer value, its value is used to determine logical
869 .B MKE2FS_DEVICE_PHYS_SECTSIZE
870 If set to non-zero integer value, its value is used to determine physical
874 .B MKE2FS_SKIP_CHECK_MSG
875 If set, do not show the message of file system automatic check caused by
876 mount count or check interval.
880 has been written by Theodore Ts'o <tytso@mit.edu>.
883 is part of the e2fsprogs package and is available from
884 http://e2fsprogs.sourceforge.net.