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 1024,
211 2048 and 4096 bytes per block. If omitted,
212 block-size is heuristically determined by the filesystem size and
213 the expected usage of the filesystem (see the
217 is preceded by a negative sign ('-'), then
219 will use heuristics to determine the
220 appropriate block size, with the constraint that the block size will be
223 bytes. This is useful for certain hardware devices which require that
224 the blocksize be a multiple of 2k.
227 Check the device for bad blocks before creating the file system. If
228 this option is specified twice, then a slower read-write
229 test is used instead of a fast read-only test.
231 .B \-C " cluster-size"
232 Specify the size of cluster in bytes for filesystems using the bigalloc
233 feature. Valid cluster-size values are from 2048 to 256M bytes per
234 cluster. This can only be specified if the bigalloc feature is
237 man page for more details about bigalloc.) The default cluster size if
238 bigalloc is enabled is 16 times the block size.
241 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
242 lot of buffer cache memory, which may impact other applications running
243 on a busy server. This option will cause mke2fs to run much more
244 slowly, however, so there is a tradeoff to using direct I/O.
246 .BI \-e " error-behavior"
247 Change the behavior of the kernel code when errors are detected.
248 In all cases, a filesystem error will cause
250 to check the filesystem on the next boot.
252 can be one of the following:
256 Continue normal execution.
259 Remount filesystem read-only.
262 Cause a kernel panic.
265 .BI \-E " extended-options"
266 Set extended options for the filesystem. Extended options are comma
267 separated, and may take an argument using the equals ('=') sign. The
271 in earlier versions of
275 option is still accepted for backwards compatibility, but is deprecated.
276 The following extended options are supported:
279 .BI mmp_update_interval= interval
280 Adjust the initial MMP update interval to
282 seconds. Specifying an
284 of 0 means to use the default interval. The specified interval must
285 be less than 300 seconds. Requires that the
289 .BI stride= stride-size
290 Configure the filesystem for a RAID array with
292 filesystem blocks. This is the number of blocks read or written to disk
293 before moving to the next disk, which is sometimes referred to as the
295 This mostly affects placement of filesystem metadata like bitmaps at
297 time to avoid placing them on a single disk, which can hurt performance.
298 It may also be used by the block allocator.
300 .BI stripe_width= stripe-width
301 Configure the filesystem for a RAID array with
303 filesystem blocks per stripe. This is typically stride-size * N, where
304 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
305 parity disk, so N will be the number of disks in the array minus 1).
306 This allows the block allocator to prevent read-modify-write of the
307 parity in a RAID stripe if possible when the data is written.
310 Create the filesystem at an offset from the beginning of the device or
311 file. This can be useful when creating disk images for virtual machines.
313 .BI resize= max-online-resize
314 Reserve enough space so that the block group descriptor table can grow
315 to support a filesystem that has
319 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
320 If enabled and the uninit_bg feature is enabled, the inode table will
321 not be fully initialized by
323 This speeds up filesystem
324 initialization noticeably, but it requires the kernel to finish
325 initializing the filesystem in the background when the filesystem is
326 first mounted. If the option value is omitted, it defaults to 1 to
327 enable lazy inode table zeroing.
329 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
330 If enabled, the journal inode will not be fully zeroed out by
332 This speeds up filesystem initialization noticeably, but carries some
333 small risk if the system crashes before the journal has been overwritten
334 entirely one time. If the option value is omitted, it defaults to 1 to
335 enable lazy journal inode zeroing.
337 .BI num_backup_sb= <0|1|2>
340 file system feature is enabled this option controls whether there will
341 be 0, 1, or 2 backup superblocks created in the file system.
343 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
344 Place the allocation bitmaps and the inode table at the beginning of the
345 disk. This option requires that the flex_bg file system feature to be
346 enabled in order for it to have effect, and will also create the journal
347 at the beginning of the file system. This option is useful for flash
348 devices that use SLC flash at the beginning of the disk.
349 It also maximizes the range of contiguous data blocks, which
350 can be useful for certain specialized use cases, such as supported
353 .BI root_owner [=uid:gid]
354 Specify the numeric user and group ID of the root directory. If no UID:GID
355 is specified, use the user and group ID of the user running \fBmke2fs\fR.
356 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
357 set by default to the UID and GID of the user running the mke2fs command.
358 The \fBroot_owner=\fR option allows explicitly specifying these values,
359 and avoid side-effects for users that do not expect the contents of the
360 filesystem to change based on the user running \fBmke2fs\fR.
363 Set a flag in the filesystem superblock indicating that it may be
364 mounted using experimental kernel code, such as the ext4dev filesystem.
367 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
368 on solid state devices and sparse / thin-provisioned storage). When the device
369 advertises that discard also zeroes data (any subsequent read after the discard
370 and before write returns zero), then mark all not-yet-zeroed inode tables as
371 zeroed. This significantly speeds up filesystem initialization. This is set
375 Do not attempt to discard blocks at mkfs time.
376 @QUOTA_MAN_COMMENT@.TP
377 @QUOTA_MAN_COMMENT@.BI quotatype
378 @QUOTA_MAN_COMMENT@Specify which quota type ('usr' or 'grp') is to be
379 @QUOTA_MAN_COMMENT@initialized. This option has effect only if the
380 @QUOTA_MAN_COMMENT@.B quota
381 @QUOTA_MAN_COMMENT@feature is set. Without this extended option, the default
382 @QUOTA_MAN_COMMENT@behavior is to initialize both user and group quotas.
385 .BI \-f " fragment-size"
386 Specify the size of fragments in bytes.
391 to create a filesystem, even if the specified device is not a partition
392 on a block special device, or if other parameters do not make sense.
395 to create a filesystem even if the filesystem appears to be in use
396 or is mounted (a truly dangerous thing to do), this option must be
399 .BI \-g " blocks-per-group"
400 Specify the number of blocks in a block group. There is generally no
401 reason for the user to ever set this parameter, as the default is optimal
402 for the filesystem. (For administrators who are creating
403 filesystems on RAID arrays, it is preferable to use the
405 RAID parameter as part of the
407 option rather than manipulating the number of blocks per group.)
408 This option is generally used by developers who
409 are developing test cases.
411 If the bigalloc feature is enabled, the
413 option will specify the number of clusters in a block group.
415 .BI \-G " number-of-groups"
416 Specify the number of block groups that will be packed together to
417 create a larger virtual block group (or "flex_bg group") in an
418 ext4 filesystem. This improves meta-data locality and performance
419 on meta-data heavy workloads. The number of groups must be a power
420 of 2 and may only be specified if the
422 filesystem feature is enabled.
424 .BI \-i " bytes-per-inode"
425 Specify the bytes/inode ratio.
427 creates an inode for every
429 bytes of space on the disk. The larger the
431 ratio, the fewer inodes will be created. This value generally shouldn't
432 be smaller than the blocksize of the filesystem, since in that case more
433 inodes would be made than can ever be used. Be warned that it is not
434 possible to change this ratio on a filesystem after it is created, so be
435 careful deciding the correct value for this parameter. Note that resizing
436 a filesystem changes the numer of inodes to maintain this ratio.
438 .BI \-I " inode-size"
439 Specify the size of each inode in bytes.
442 value must be a power of 2 larger or equal to 128. The larger the
444 the more space the inode table will consume, and this reduces the usable
445 space in the filesystem and can also negatively impact performance.
447 possible to change this value after the filesystem is created.
449 In kernels after 2.6.10 and some
450 earlier vendor kernels it is possible to utilize inodes larger than
452 extended attributes for improved performance.
454 stored in large inodes are not visible with older kernels, and such
455 filesystems will not be mountable with 2.4 kernels at all.
457 The default inode size is controlled by the
461 file shipped with e2fsprogs, the default inode size is 256 bytes for
462 most file systems, except for small file systems where the inode size
466 Create the filesystem with an ext3 journal. If the
468 option is not specified, the default journal parameters will be used to
469 create an appropriately sized journal (given the size of the filesystem)
470 stored within the filesystem. Note that you must be using a kernel
471 which has ext3 support in order to actually make use of the journal.
473 .BI \-J " journal-options"
474 Create the ext3 journal using options specified on the command-line.
475 Journal options are comma
476 separated, and may take an argument using the equals ('=') sign.
477 The following journal options are supported:
480 .BI size= journal-size
481 Create an internal journal (i.e., stored inside the filesystem) of size
484 The size of the journal must be at least 1024 filesystem blocks
485 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
486 and may be no more than 10,240,000 filesystem blocks or half the total
487 file system size (whichever is smaller)
489 .BI location =journal-location
490 Specify the location of the journal. The argument
492 can either be specified as a block number, or if the number has a units
493 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
494 beginning of the file system.
496 @JDEV@.BI device= external-journal
497 @JDEV@Attach the filesystem to the journal block device located on
498 @JDEV@.IR external-journal .
500 @JDEV@journal must already have been created using the command
502 @JDEV@.B mke2fs -O journal_dev
503 @JDEV@.I external-journal
506 @JDEV@.I external-journal
507 @JDEV@must have been created with the
508 @JDEV@same block size as the new filesystem.
509 @JDEV@In addition, while there is support for attaching
510 @JDEV@multiple filesystems to a single external journal,
511 @JDEV@the Linux kernel and
513 @JDEV@do not currently support shared external journals yet.
515 @JDEV@Instead of specifying a device name directly,
516 @JDEV@.I external-journal
517 @JDEV@can also be specified by either
518 @JDEV@.BI LABEL= label
521 @JDEV@to locate the external journal by either the volume label or UUID
522 @JDEV@stored in the ext2 superblock at the start of the journal. Use
523 @JDEV@.BR dumpe2fs (8)
524 @JDEV@to display a journal device's volume label and UUID. See also the
527 @JDEV@.BR tune2fs (8).
530 @JDEV@Only one of the
531 @JDEV@.BR size " or " device
532 @JDEV@options can be given for a filesystem.
535 Read the bad blocks list from
537 Note that the block numbers in the bad block list must be generated
538 using the same block size as used by
544 is a much simpler and less error-prone method of checking a disk for bad
545 blocks before formatting it, as
547 will automatically pass the correct parameters to the
551 .BI \-L " new-volume-label"
552 Set the volume label for the filesystem to
553 .IR new-volume-label .
554 The maximum length of the
555 volume label is 16 bytes.
557 .BI \-m " reserved-blocks-percentage"
558 Specify the percentage of the filesystem blocks reserved for
559 the super-user. This avoids fragmentation, and allows root-owned
562 to continue to function correctly after non-privileged processes are
563 prevented from writing to the filesystem. The default percentage
566 .BI \-M " last-mounted-directory"
567 Set the last mounted directory for the filesystem. This might be useful
568 for the sake of utilities that key off of the last mounted directory to
569 determine where the filesystem should be mounted.
574 to not actually create a filesystem, but display what it
575 would do if it were to create a filesystem. This can be used to
576 determine the location of the backup superblocks for a particular
577 filesystem, so long as the
579 parameters that were passed when the
580 filesystem was originally created are used again. (With the
582 option added, of course!)
584 .BI \-N " number-of-inodes"
585 Overrides the default calculation of the number of inodes that should be
586 reserved for the filesystem (which is based on the number of blocks and
589 ratio). This allows the user to specify the number
590 of desired inodes directly.
592 .BI \-d " root-directory"
593 Add the files from the root-directory to the filesystem.
595 .BI \-o " creator-os"
596 Overrides the default value of the "creator operating system" field of the
597 filesystem. The creator field is set by default to the name of the OS the
599 executable was compiled for.
601 .B "\-O \fR[^]\fIfeature\fR[,...]"
602 Create a filesystem with the given features (filesystem options),
603 overriding the default filesystem options. The features that are
604 enabled by default are specified by the
606 relation, either in the
613 subsections for the usage types as specified by the
615 option, further modified by the
617 relation found in the
619 subsections for the filesystem and usage types. See the
621 manual page for more details.
622 The filesystem type-specific configuration setting found in the
624 section will override the global default found in
627 The filesystem feature set will be further edited
628 using either the feature set specified by this option,
629 or if this option is not given, by the
631 relation for the filesystem type being created, or in the
633 section of the configuration file.
635 The filesystem feature set is comprised of a list of features, separated
636 by commas, that are to be enabled. To disable a feature, simply
637 prefix the feature name with a caret ('^') character.
638 Features with dependencies will not be removed successfully.
639 The pseudo-filesystem feature "none" will clear all filesystem features.
641 For more information about the features which can be set, please see
646 Quiet execution. Useful if
651 Set the filesystem revision for the new filesystem. Note that 1.2
652 kernels only support revision 0 filesystems. The default is to
653 create revision 1 filesystems.
656 Write superblock and group descriptors only. This is useful if all of
657 the superblock and backup superblocks are corrupted, and a last-ditch
658 recovery method is desired. It causes
661 superblock and group descriptors, while not touching the inode table
662 and the block and inode bitmaps. The
664 program should be run immediately after this option is used, and there
665 is no guarantee that any data will be salvageable. It is critical to
666 specify the correct filesystem blocksize when using this option,
667 or there is no chance of recovery.
670 .\" Check the device for bad blocks before creating the file system
671 .\" using the specified test.
674 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
676 If this option is not specified,
678 will pick a default either via how
679 the command was run (for example, using a name of the form mkfs.ext2,
680 mkfs.ext3, etc.) or via a default as defined by the
682 file. This option controls which filesystem options are used by
683 default, based on the
685 configuration stanza in
686 .BR /etc/mke2fs.conf .
690 option is used to explicitly add or remove filesystem options that
691 should be set in the newly created filesystem, the
692 resulting filesystem may not be supported by the requested
694 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
695 filesystem that is not supported by the ext3 implementation as found in
696 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
697 will create a filesystem that does not have a journal and hence will not
698 be supported by the ext3 filesystem code in the Linux kernel.)
700 .BI \-T " usage-type[,...]"
701 Specify how the filesystem is going to be used, so that
703 can choose optimal filesystem parameters for that use. The usage
704 types that are supported are defined in the configuration file
705 .BR /etc/mke2fs.conf .
706 The user may specify one or more usage types
707 using a comma separated list.
709 If this option is is not specified,
711 will pick a single default usage type based on the size of the filesystem to
712 be created. If the filesystem size is less than 3 megabytes,
714 will use the filesystem type
716 If the filesystem size is greater than or equal to 3 but less than
719 will use the filesystem type
721 If the filesystem size is greater than or equal to 4 terabytes but less than
724 will use the filesystem type
726 If the filesystem size is greater than or equal to 16 terabytes,
728 will use the filesystem type
732 will use the default filesystem type
736 Create the filesystem with the specified UUID.
742 Print the version number of
747 Before overwriting a file system block, write the old contents of the block to
748 an undo file. This undo file can be used with e2undo(8) to restore the old
749 contents of the file system should something go wrong. If the empty string is
750 passed as the undo_file argument, the undo file will be written to a file named
751 mke2fs-\fIdevice\fR.e2undo in the directory specified via the
752 \fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
753 in the configuration file.
755 WARNING: The undo file cannot be used to recover from a power or system crash.
759 If set to non-zero integer value, its value is used to determine how often
761 is called during inode table initialization.
764 Determines the location of the configuration file (see
765 .BR mke2fs.conf (5)).
767 .BI MKE2FS_FIRST_META_BG
768 If set to non-zero integer value, its value is used to determine first meta
769 block group. This is mostly for debugging purposes.
771 .BI MKE2FS_DEVICE_SECTSIZE
772 If set to non-zero integer value, its value is used to determine physical
776 .BI MKE2FS_SKIP_CHECK_MSG
777 If set, do not show the message of filesystem automatic check caused by
778 mount count or check interval.
782 has been written by Theodore Ts'o <tytso@mit.edu>.
787 option but currently ignores it because the second
788 extended file system does not support fragments yet.
790 There may be other ones. Please, report them to the author.
793 is part of the e2fsprogs package and is available from
794 http://e2fsprogs.sourceforge.net.