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
67 .I reserved-blocks-percentage
75 [^]\fIfeature\fR[,...]
100 .I last-mounted-directory
133 @JDEV@.B "mke2fs \-O journal_dev"
138 .\" No external-journal specific journal options yet (size is ignored)
141 .\" @JDEV@.I journal-options
145 @JDEV@.I volume-label
156 @JDEV@.I external-journal
162 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
163 partition (or file) named by
166 The file system size is specified by
170 does not have a suffix, it is interpreted as power-of-two kilobytes,
174 option is specified, in which case
176 is interpreted as the number of
178 blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't'
179 (either upper-case or lower-case), then it is interpreted in
180 power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
185 will create the file system based on the device size.
201 will create a file system for use with ext3,
203 will create a file system for use with ext4, and so on.
205 The defaults of the parameters for the newly created filesystem, if not
206 overridden by the options listed below, are controlled by the
208 configuration file. See the
210 manual page for more details.
213 .BI \-b " block-size"
214 Specify the size of blocks in bytes. Valid block-size values are powers of two
215 from 1024 up to 65536 (however note that the kernel is able to mount only
216 filesystems with block-size smaller or equal to the system page size - 4k on
217 x86 systems, up to 64k on ppc64 or aarch64 depending on kernel configuration).
218 If omitted, block-size is heuristically determined by the filesystem size and
219 the expected usage of the filesystem (see the
221 option). In most common cases, the default block size is 4k. If
223 is preceded by a negative sign ('-'), then
225 will use heuristics to determine the
226 appropriate block size, with the constraint that the block size will be
229 bytes. This is useful for certain hardware devices which require that
230 the blocksize be a multiple of 2k.
233 Check the device for bad blocks before creating the file system. If
234 this option is specified twice, then a slower read-write
235 test is used instead of a fast read-only test.
237 .B \-C " cluster-size"
238 Specify the size of cluster in bytes for filesystems using the bigalloc
239 feature. Valid cluster-size values are from 2048 to 256M bytes per
240 cluster. This can only be specified if the bigalloc feature is
243 man page for more details about bigalloc.) The default cluster size if
244 bigalloc is enabled is 16 times the block size.
246 .BI \-d " root-directory"
247 Copy the contents of the given directory into the root directory of the
251 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
252 lot of buffer cache memory, which may impact other applications running
253 on a busy server. This option will cause mke2fs to run much more
254 slowly, however, so there is a tradeoff to using direct I/O.
256 .BI \-e " error-behavior"
257 Change the behavior of the kernel code when errors are detected.
258 In all cases, a filesystem error will cause
260 to check the filesystem on the next boot.
262 can be one of the following:
266 Continue normal execution.
269 Remount filesystem read-only.
272 Cause a kernel panic.
275 .BI \-E " extended-options"
276 Set extended options for the filesystem. Extended options are comma
277 separated, and may take an argument using the equals ('=') sign. The
281 in earlier versions of
285 option is still accepted for backwards compatibility, but is deprecated.
286 The following extended options are supported:
289 .BI encoding= encoding-name
292 feature in the super block and set
294 as the encoding to be used. If
296 is not specified, the encoding defined in
300 .BI encoding_flags= encoding-flags
301 Define parameters for file name character encoding operations. If a
302 flag is not changed using this parameter, its default value is used.
304 should be a comma-separated lists of flags to be enabled. To disable a
305 flag, add it to the list with the prefix "no".
307 The only flag that can be set right now is
309 which means that invalid strings should be rejected by the file system.
310 In the default configuration, the
314 .BI mmp_update_interval= interval
315 Adjust the initial MMP update interval to
317 seconds. Specifying an
319 of 0 means to use the default interval. The specified interval must
320 be less than 300 seconds. Requires that the
324 .BI stride= stride-size
325 Configure the filesystem for a RAID array with
327 filesystem blocks. This is the number of blocks read or written to disk
328 before moving to the next disk, which is sometimes referred to as the
330 This mostly affects placement of filesystem metadata like bitmaps at
332 time to avoid placing them on a single disk, which can hurt performance.
333 It may also be used by the block allocator.
335 .BI stripe_width= stripe-width
336 Configure the filesystem for a RAID array with
338 filesystem blocks per stripe. This is typically stride-size * N, where
339 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
340 parity disk, so N will be the number of disks in the array minus 1).
341 This allows the block allocator to prevent read-modify-write of the
342 parity in a RAID stripe if possible when the data is written.
345 Create the filesystem at an offset from the beginning of the device or
346 file. This can be useful when creating disk images for virtual machines.
348 .BI resize= max-online-resize
349 Reserve enough space so that the block group descriptor table can grow
350 to support a filesystem that has
354 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
355 If enabled and the uninit_bg feature is enabled, the inode table will
356 not be fully initialized by
358 This speeds up filesystem
359 initialization noticeably, but it requires the kernel to finish
360 initializing the filesystem in the background when the filesystem is
361 first mounted. If the option value is omitted, it defaults to 1 to
362 enable lazy inode table zeroing.
364 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
365 If enabled, the journal inode will not be fully zeroed out by
367 This speeds up filesystem initialization noticeably, but carries some
368 small risk if the system crashes before the journal has been overwritten
369 entirely one time. If the option value is omitted, it defaults to 1 to
370 enable lazy journal inode zeroing.
375 will copy the extended attributes of the files in the directory
376 hierarchy specified via the (optional)
378 option. This will disable the copy and leaves the files in the newly
379 created file system without any extended attributes.
381 .BI num_backup_sb= <0|1|2>
384 file system feature is enabled this option controls whether there will
385 be 0, 1, or 2 backup superblocks created in the file system.
387 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
388 Place the allocation bitmaps and the inode table at the beginning of the
389 disk. This option requires that the flex_bg file system feature to be
390 enabled in order for it to have effect, and will also create the journal
391 at the beginning of the file system. This option is useful for flash
392 devices that use SLC flash at the beginning of the disk.
393 It also maximizes the range of contiguous data blocks, which
394 can be useful for certain specialized use cases, such as supported
397 .BI root_owner [=uid:gid]
398 Specify the numeric user and group ID of the root directory. If no UID:GID
399 is specified, use the user and group ID of the user running \fBmke2fs\fR.
400 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
401 set by default to the UID and GID of the user running the mke2fs command.
402 The \fBroot_owner=\fR option allows explicitly specifying these values,
403 and avoid side-effects for users that do not expect the contents of the
404 filesystem to change based on the user running \fBmke2fs\fR.
407 Set a flag in the filesystem superblock indicating that it may be
408 mounted using experimental kernel code, such as the ext4dev filesystem.
411 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
412 on solid state devices and sparse / thin-provisioned storage). When the device
413 advertises that discard also zeroes data (any subsequent read after the discard
414 and before write returns zero), then mark all not-yet-zeroed inode tables as
415 zeroed. This significantly speeds up filesystem initialization. This is set
419 Do not attempt to discard blocks at mkfs time.
422 Specify the which quota types (usrquota, grpquota, prjquota) which
423 should be enabled in the created file system. The argument of this
424 extended option should be a colon separated list. This option has
427 feature is set. The default quota types to be initialized if this
428 option is not specified is both user and group quotas. If the project
429 feature is enabled that project quotas will be initialized as well.
435 to create a filesystem, even if the specified device is not a partition
436 on a block special device, or if other parameters do not make sense.
439 to create a filesystem even if the filesystem appears to be in use
440 or is mounted (a truly dangerous thing to do), this option must be
443 .BI \-g " blocks-per-group"
444 Specify the number of blocks in a block group. There is generally no
445 reason for the user to ever set this parameter, as the default is optimal
446 for the filesystem. (For administrators who are creating
447 filesystems on RAID arrays, it is preferable to use the
449 RAID parameter as part of the
451 option rather than manipulating the number of blocks per group.)
452 This option is generally used by developers who
453 are developing test cases.
455 If the bigalloc feature is enabled, the
457 option will specify the number of clusters in a block group.
459 .BI \-G " number-of-groups"
460 Specify the number of block groups that will be packed together to
461 create a larger virtual block group (or "flex_bg group") in an
462 ext4 filesystem. This improves meta-data locality and performance
463 on meta-data heavy workloads. The number of groups must be a power
464 of 2 and may only be specified if the
466 filesystem feature is enabled.
468 .BI \-i " bytes-per-inode"
469 Specify the bytes/inode ratio.
471 creates an inode for every
473 bytes of space on the disk. The larger the
475 ratio, the fewer inodes will be created. This value generally shouldn't
476 be smaller than the blocksize of the filesystem, since in that case more
477 inodes would be made than can ever be used. Be warned that it is not
478 possible to change this ratio on a filesystem after it is created, so be
479 careful deciding the correct value for this parameter. Note that resizing
480 a filesystem changes the number of inodes to maintain this ratio.
482 .BI \-I " inode-size"
483 Specify the size of each inode in bytes.
486 value must be a power of 2 larger or equal to 128. The larger the
488 the more space the inode table will consume, and this reduces the usable
489 space in the filesystem and can also negatively impact performance.
491 possible to change this value after the filesystem is created.
493 File systems with an inode size of 128 bytes do not support timestamps
494 beyond January 19, 2038. Inodes which are 256 bytes or larger will
495 support extended timestamps, project id's, and the ability to store some
496 extended attributes in the inode table for improved performance.
498 The default inode size is controlled by the
502 file shipped with e2fsprogs, the default inode size is 256 bytes for
503 most file systems, except for small file systems where the inode size
507 Create the filesystem with an ext3 journal. If the
509 option is not specified, the default journal parameters will be used to
510 create an appropriately sized journal (given the size of the filesystem)
511 stored within the filesystem. Note that you must be using a kernel
512 which has ext3 support in order to actually make use of the journal.
514 .BI \-J " journal-options"
515 Create the ext3 journal using options specified on the command-line.
516 Journal options are comma
517 separated, and may take an argument using the equals ('=') sign.
518 The following journal options are supported:
521 .BI size= journal-size
522 Create an internal journal (i.e., stored inside the filesystem) of size
525 The size of the journal must be at least 1024 filesystem blocks
526 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
527 and may be no more than 10,240,000 filesystem blocks or half the total
528 file system size (whichever is smaller)
530 .BI fast_commit_size= fast-commit-size
531 Create an additional fast commit journal area of size
534 This option is only valid if
537 on the file system. If this option is not specified and if
539 feature is turned on, fast commit area size defaults to
541 / 64 megabytes. The total size of the journal with
547 * 1024) megabytes. The total journal size may be no more than
548 10,240,000 filesystem blocks or half the total file system size
549 (whichever is smaller).
551 .BI location =journal-location
552 Specify the location of the journal. The argument
554 can either be specified as a block number, or if the number has a units
555 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
556 beginning of the file system.
558 @JDEV@.BI device= external-journal
559 @JDEV@Attach the filesystem to the journal block device located on
560 @JDEV@.IR external-journal .
562 @JDEV@journal must already have been created using the command
564 @JDEV@.B mke2fs -O journal_dev
565 @JDEV@.I external-journal
568 @JDEV@.I external-journal
569 @JDEV@must have been created with the
570 @JDEV@same block size as the new filesystem.
571 @JDEV@In addition, while there is support for attaching
572 @JDEV@multiple filesystems to a single external journal,
573 @JDEV@the Linux kernel and
575 @JDEV@do not currently support shared external journals yet.
577 @JDEV@Instead of specifying a device name directly,
578 @JDEV@.I external-journal
579 @JDEV@can also be specified by either
580 @JDEV@.BI LABEL= label
583 @JDEV@to locate the external journal by either the volume label or UUID
584 @JDEV@stored in the ext2 superblock at the start of the journal. Use
585 @JDEV@.BR dumpe2fs (8)
586 @JDEV@to display a journal device's volume label and UUID. See also the
589 @JDEV@.BR tune2fs (8).
592 @JDEV@Only one of the
593 @JDEV@.BR size " or " device
594 @JDEV@options can be given for a filesystem.
597 Read the bad blocks list from
599 Note that the block numbers in the bad block list must be generated
600 using the same block size as used by
606 is a much simpler and less error-prone method of checking a disk for bad
607 blocks before formatting it, as
609 will automatically pass the correct parameters to the
613 .BI \-L " new-volume-label"
614 Set the volume label for the filesystem to
615 .IR new-volume-label .
616 The maximum length of the
617 volume label is 16 bytes.
619 .BI \-m " reserved-blocks-percentage"
620 Specify the percentage of the filesystem blocks reserved for
621 the super-user. This avoids fragmentation, and allows root-owned
624 to continue to function correctly after non-privileged processes are
625 prevented from writing to the filesystem. The default percentage
628 .BI \-M " last-mounted-directory"
629 Set the last mounted directory for the filesystem. This might be useful
630 for the sake of utilities that key off of the last mounted directory to
631 determine where the filesystem should be mounted.
636 to not actually create a filesystem, but display what it
637 would do if it were to create a filesystem. This can be used to
638 determine the location of the backup superblocks for a particular
639 filesystem, so long as the
641 parameters that were passed when the
642 filesystem was originally created are used again. (With the
644 option added, of course!)
646 .BI \-N " number-of-inodes"
647 Overrides the default calculation of the number of inodes that should be
648 reserved for the filesystem (which is based on the number of blocks and
651 ratio). This allows the user to specify the number
652 of desired inodes directly.
654 .BI \-d " root-directory"
655 Add the files from the root-directory to the filesystem.
657 .BI \-o " creator-os"
658 Overrides the default value of the "creator operating system" field of the
659 filesystem. The creator field is set by default to the name of the OS the
661 executable was compiled for.
663 .B "\-O \fR[^]\fIfeature\fR[,...]"
664 Create a filesystem with the given features (filesystem options),
665 overriding the default filesystem options. The features that are
666 enabled by default are specified by the
668 relation, either in the
675 subsections for the usage types as specified by the
677 option, further modified by the
679 relation found in the
681 subsections for the filesystem and usage types. See the
683 manual page for more details.
684 The filesystem type-specific configuration setting found in the
686 section will override the global default found in
689 The filesystem feature set will be further edited
690 using either the feature set specified by this option,
691 or if this option is not given, by the
693 relation for the filesystem type being created, or in the
695 section of the configuration file.
697 The filesystem feature set is comprised of a list of features, separated
698 by commas, that are to be enabled. To disable a feature, simply
699 prefix the feature name with a caret ('^') character.
700 Features with dependencies will not be removed successfully.
701 The pseudo-filesystem feature "none" will clear all filesystem features.
703 For more information about the features which can be set, please see
708 Quiet execution. Useful if
713 Set the filesystem revision for the new filesystem. Note that 1.2
714 kernels only support revision 0 filesystems. The default is to
715 create revision 1 filesystems.
718 Write superblock and group descriptors only. This is an extreme
719 measure to be taken only in the very unlikely case that all of
720 the superblock and backup superblocks are corrupted, and a last-ditch
721 recovery method is desired by experienced users. It causes
723 to reinitialize the superblock and group descriptors, while not
724 touching the inode table and the block and inode bitmaps. The
726 program should be run immediately after this option is used, and there
727 is no guarantee that any data will be salvageable. Due to the wide
728 variety of possible options to
730 that affect the on-disk layout, it is critical to specify exactly
731 the same format options, such as blocksize, fs-type, feature flags, and
732 other tunables when using this option, or the filesystem will be further
733 corrupted. In some cases, such as filesystems that have been resized,
734 or have had features enabled after format time, it is impossible to
735 overwrite all of the superblocks correctly, and at least some filesystem
736 corruption will occur. It is best to run this on a full copy of the
737 filesystem so other options can be tried if this doesn't work.
740 .\" Check the device for bad blocks before creating the file system
741 .\" using the specified test.
744 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
746 If this option is not specified,
748 will pick a default either via how
749 the command was run (for example, using a name of the form mkfs.ext2,
750 mkfs.ext3, etc.) or via a default as defined by the
752 file. This option controls which filesystem options are used by
753 default, based on the
755 configuration stanza in
756 .BR /etc/mke2fs.conf .
760 option is used to explicitly add or remove filesystem options that
761 should be set in the newly created filesystem, the
762 resulting filesystem may not be supported by the requested
764 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
765 filesystem that is not supported by the ext3 implementation as found in
766 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
767 will create a filesystem that does not have a journal and hence will not
768 be supported by the ext3 filesystem code in the Linux kernel.)
770 .BI \-T " usage-type[,...]"
771 Specify how the filesystem is going to be used, so that
773 can choose optimal filesystem parameters for that use. The usage
774 types that are supported are defined in the configuration file
775 .BR /etc/mke2fs.conf .
776 The user may specify one or more usage types
777 using a comma separated list.
779 If this option is is not specified,
781 will pick a single default usage type based on the size of the filesystem to
782 be created. If the filesystem size is less than 3 megabytes,
784 will use the filesystem type
786 If the filesystem size is greater than or equal to 3 but less than
789 will use the filesystem type
791 If the filesystem size is greater than or equal to 4 terabytes but less than
794 will use the filesystem type
796 If the filesystem size is greater than or equal to 16 terabytes,
798 will use the filesystem type
802 will use the default filesystem type
806 Set the universally unique identifier (UUID) of the filesystem to
808 The format of the UUID is a series of hex digits separated by hyphens,
810 "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
813 parameter may also be one of the following:
817 clear the filesystem UUID
820 generate a new randomly-generated UUID
823 generate a new time-based UUID
830 Print the version number of
835 Before overwriting a file system block, write the old contents of the block to
836 an undo file. This undo file can be used with e2undo(8) to restore the old
837 contents of the file system should something go wrong. If the empty string is
838 passed as the undo_file argument, the undo file will be written to a file named
839 mke2fs-\fIdevice\fR.e2undo in the directory specified via the
840 \fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
841 in the configuration file.
843 WARNING: The undo file cannot be used to recover from a power or system crash.
847 If set to non-zero integer value, its value is used to determine how often
849 is called during inode table initialization.
852 Determines the location of the configuration file (see
853 .BR mke2fs.conf (5)).
855 .B MKE2FS_FIRST_META_BG
856 If set to non-zero integer value, its value is used to determine first meta
857 block group. This is mostly for debugging purposes.
859 .B MKE2FS_DEVICE_SECTSIZE
860 If set to non-zero integer value, its value is used to determine logical
864 .B MKE2FS_DEVICE_PHYS_SECTSIZE
865 If set to non-zero integer value, its value is used to determine physical
869 .B MKE2FS_SKIP_CHECK_MSG
870 If set, do not show the message of filesystem automatic check caused by
871 mount count or check interval.
875 has been written by Theodore Ts'o <tytso@mit.edu>.
878 is part of the e2fsprogs package and is available from
879 http://e2fsprogs.sourceforge.net.