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
59 .I reserved-blocks-percentage
67 [^]\fIfeature\fR[,...]
92 .I last-mounted-directory
117 @JDEV@.B "mke2fs \-O journal_dev"
122 .\" No external-journal specific journal options yet (size is ignored)
125 .\" @JDEV@.I journal-options
129 @JDEV@.I volume-label
140 @JDEV@.I external-journal
146 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
147 partition (or file) named by
150 The file system size is specified by
154 does not have a suffix, it is interpreted as power-of-two kilobytes,
158 option is specified, in which case
160 is interpreted as the number of
162 blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't'
163 (either upper-case or lower-case), then it is interpreted in
164 power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
169 will create the file system based on the device size.
185 will create a file system for use with ext3,
187 will create a file system for use with ext4, and so on.
189 The defaults of the parameters for the newly created filesystem, if not
190 overridden by the options listed below, are controlled by the
192 configuration file. See the
194 manual page for more details.
197 .BI \-b " block-size"
198 Specify the size of blocks in bytes. Valid block-size values are 1024,
199 2048 and 4096 bytes per block. If omitted,
200 block-size is heuristically determined by the filesystem size and
201 the expected usage of the filesystem (see the
205 is preceded by a negative sign ('-'), then
207 will use heuristics to determine the
208 appropriate block size, with the constraint that the block size will be
211 bytes. This is useful for certain hardware devices which require that
212 the blocksize be a multiple of 2k.
215 Check the device for bad blocks before creating the file system. If
216 this option is specified twice, then a slower read-write
217 test is used instead of a fast read-only test.
219 .B \-C " cluster-size"
220 Specify the size of cluster in bytes for filesystems using the bigalloc
221 feature. Valid cluster-size values are from 2048 to 256M bytes per
222 cluster. This can only be specified if the bigalloc feature is
225 man page for more details about bigalloc.) The default cluster size if
226 bigalloc is enabled is 16 times the block size.
229 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
230 lot of buffer cache memory, which may impact other applications running
231 on a busy server. This option will cause mke2fs to run much more
232 slowly, however, so there is a tradeoff to using direct I/O.
234 .BI \-E " extended-options"
235 Set extended options for the filesystem. Extended options are comma
236 separated, and may take an argument using the equals ('=') sign. The
240 in earlier versions of
244 option is still accepted for backwards compatibility, but is deprecated.
245 The following extended options are supported:
248 .BI mmp_update_interval= interval
249 Adjust the initial MMP update interval to
251 seconds. Specifying an
253 of 0 means to use the default interval. The specified interval must
254 be less than 300 seconds. Requires that the
258 .BI stride= stride-size
259 Configure the filesystem for a RAID array with
261 filesystem blocks. This is the number of blocks read or written to disk
262 before moving to the next disk, which is sometimes referred to as the
264 This mostly affects placement of filesystem metadata like bitmaps at
266 time to avoid placing them on a single disk, which can hurt performance.
267 It may also be used by the block allocator.
269 .BI stripe_width= stripe-width
270 Configure the filesystem for a RAID array with
272 filesystem blocks per stripe. This is typically stride-size * N, where
273 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
274 parity disk, so N will be the number of disks in the array minus 1).
275 This allows the block allocator to prevent read-modify-write of the
276 parity in a RAID stripe if possible when the data is written.
279 Create the filesystem at an offset from the beginning of the device or
280 file. This can be useful when creating disk images for virtual machines.
282 .BI resize= max-online-resize
283 Reserve enough space so that the block group descriptor table can grow
284 to support a filesystem that has
288 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
289 If enabled and the uninit_bg feature is enabled, the inode table will
290 not be fully initialized by
292 This speeds up filesystem
293 initialization noticeably, but it requires the kernel to finish
294 initializing the filesystem in the background when the filesystem is
295 first mounted. If the option value is omitted, it defaults to 1 to
296 enable lazy inode table zeroing.
298 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
299 If enabled, the journal inode will not be fully zeroed out by
301 This speeds up filesystem initialization noticeably, but carries some
302 small risk if the system crashes before the journal has been overwritten
303 entirely one time. If the option value is omitted, it defaults to 1 to
304 enable lazy journal inode zeroing.
306 .BI num_backup_sb= <0|1|2>
309 file system feature is enabled this option controls whether there will
310 be 0, 1, or 2 backup superblocks created in the file system.
312 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
313 Place the allocation bitmaps and the inode table at the beginning of the
314 disk. This option requires that the flex_bg file system feature to be
315 enabled in order for it to have effect, and will also create the journal
316 at the beginning of the file system. This option is useful for flash
317 devices that use SLC flash at the beginning of the disk.
318 It also maximizes the range of contiguous data blocks, which
319 can be useful for certain specialized use cases, such as supported
322 .BI root_owner [=uid:gid]
323 Specify the numeric user and group ID of the root directory. If no UID:GID
324 is specified, use the user and group ID of the user running \fBmke2fs\fR.
325 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
326 set by default to the UID and GID of the user running the mke2fs command.
327 The \fBroot_owner=\fR option allows explicitly specifying these values,
328 and avoid side-effects for users that do not expect the contents of the
329 filesystem to change based on the user running \fBmke2fs\fR.
332 Set a flag in the filesystem superblock indicating that it may be
333 mounted using experimental kernel code, such as the ext4dev filesystem.
336 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
337 on solid state devices and sparse / thin-provisioned storage). When the device
338 advertises that discard also zeroes data (any subsequent read after the discard
339 and before write returns zero), then mark all not-yet-zeroed inode tables as
340 zeroed. This significantly speeds up filesystem initialization. This is set
344 Do not attempt to discard blocks at mkfs time.
345 @QUOTA_MAN_COMMENT@.TP
346 @QUOTA_MAN_COMMENT@.BI quotatype
347 @QUOTA_MAN_COMMENT@Specify which quota type ('usr' or 'grp') is to be
348 @QUOTA_MAN_COMMENT@initialized. This option has effect only if the
349 @QUOTA_MAN_COMMENT@.B quota
350 @QUOTA_MAN_COMMENT@feature is set. Without this extended option, the default
351 @QUOTA_MAN_COMMENT@behavior is to initialize both user and group quotas.
354 .BI \-f " fragment-size"
355 Specify the size of fragments in bytes.
360 to create a filesystem, even if the specified device is not a partition
361 on a block special device, or if other parameters do not make sense.
364 to create a filesystem even if the filesystem appears to be in use
365 or is mounted (a truly dangerous thing to do), this option must be
368 .BI \-g " blocks-per-group"
369 Specify the number of blocks in a block group. There is generally no
370 reason for the user to ever set this parameter, as the default is optimal
371 for the filesystem. (For administrators who are creating
372 filesystems on RAID arrays, it is preferable to use the
374 RAID parameter as part of the
376 option rather than manipulating the number of blocks per group.)
377 This option is generally used by developers who
378 are developing test cases.
380 If the bigalloc feature is enabled, the
382 option will specify the number of clusters in a block group.
384 .BI \-G " number-of-groups"
385 Specify the number of block groups that will be packed together to
386 create a larger virtual block group (or "flex_bg group") in an
387 ext4 filesystem. This improves meta-data locality and performance
388 on meta-data heavy workloads. The number of groups must be a power
389 of 2 and may only be specified if the
391 filesystem feature is enabled.
393 .BI \-i " bytes-per-inode"
394 Specify the bytes/inode ratio.
396 creates an inode for every
398 bytes of space on the disk. The larger the
400 ratio, the fewer inodes will be created. This value generally shouldn't
401 be smaller than the blocksize of the filesystem, since in that case more
402 inodes would be made than can ever be used. Be warned that it is not
403 possible to change this ratio on a filesystem after it is created, so be
404 careful deciding the correct value for this parameter. Note that resizing
405 a filesystem changes the numer of inodes to maintain this ratio.
407 .BI \-I " inode-size"
408 Specify the size of each inode in bytes.
411 value must be a power of 2 larger or equal to 128. The larger the
413 the more space the inode table will consume, and this reduces the usable
414 space in the filesystem and can also negatively impact performance.
416 possible to change this value after the filesystem is created.
418 In kernels after 2.6.10 and some
419 earlier vendor kernels it is possible to utilize inodes larger than
421 extended attributes for improved performance.
423 stored in large inodes are not visible with older kernels, and such
424 filesystems will not be mountable with 2.4 kernels at all.
426 The default inode size is controlled by the
430 file shipped with e2fsprogs, the default inode size is 256 bytes for
431 most file systems, except for small file systems where the inode size
435 Create the filesystem with an ext3 journal. If the
437 option is not specified, the default journal parameters will be used to
438 create an appropriately sized journal (given the size of the filesystem)
439 stored within the filesystem. Note that you must be using a kernel
440 which has ext3 support in order to actually make use of the journal.
442 .BI \-J " journal-options"
443 Create the ext3 journal using options specified on the command-line.
444 Journal options are comma
445 separated, and may take an argument using the equals ('=') sign.
446 The following journal options are supported:
449 .BI size= journal-size
450 Create an internal journal (i.e., stored inside the filesystem) of size
453 The size of the journal must be at least 1024 filesystem blocks
454 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
455 and may be no more than 10,240,000 filesystem blocks or half the total
456 file system size (whichever is smaller)
458 .BI location =journal-location
459 Specify the location of the journal. The argument
461 can either be specified as a block number, or if the number has a units
462 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
463 beginning of the file system.
465 @JDEV@.BI device= external-journal
466 @JDEV@Attach the filesystem to the journal block device located on
467 @JDEV@.IR external-journal .
469 @JDEV@journal must already have been created using the command
471 @JDEV@.B mke2fs -O journal_dev
472 @JDEV@.I external-journal
475 @JDEV@.I external-journal
476 @JDEV@must have been created with the
477 @JDEV@same block size as the new filesystem.
478 @JDEV@In addition, while there is support for attaching
479 @JDEV@multiple filesystems to a single external journal,
480 @JDEV@the Linux kernel and
482 @JDEV@do not currently support shared external journals yet.
484 @JDEV@Instead of specifying a device name directly,
485 @JDEV@.I external-journal
486 @JDEV@can also be specified by either
487 @JDEV@.BI LABEL= label
490 @JDEV@to locate the external journal by either the volume label or UUID
491 @JDEV@stored in the ext2 superblock at the start of the journal. Use
492 @JDEV@.BR dumpe2fs (8)
493 @JDEV@to display a journal device's volume label and UUID. See also the
496 @JDEV@.BR tune2fs (8).
499 @JDEV@Only one of the
500 @JDEV@.BR size " or " device
501 @JDEV@options can be given for a filesystem.
504 Read the bad blocks list from
506 Note that the block numbers in the bad block list must be generated
507 using the same block size as used by
513 is a much simpler and less error-prone method of checking a disk for bad
514 blocks before formatting it, as
516 will automatically pass the correct parameters to the
520 .BI \-L " new-volume-label"
521 Set the volume label for the filesystem to
522 .IR new-volume-label .
523 The maximum length of the
524 volume label is 16 bytes.
526 .BI \-m " reserved-blocks-percentage"
527 Specify the percentage of the filesystem blocks reserved for
528 the super-user. This avoids fragmentation, and allows root-owned
531 to continue to function correctly after non-privileged processes are
532 prevented from writing to the filesystem. The default percentage
535 .BI \-M " last-mounted-directory"
536 Set the last mounted directory for the filesystem. This might be useful
537 for the sake of utilities that key off of the last mounted directory to
538 determine where the filesystem should be mounted.
543 to not actually create a filesystem, but display what it
544 would do if it were to create a filesystem. This can be used to
545 determine the location of the backup superblocks for a particular
546 filesystem, so long as the
548 parameters that were passed when the
549 filesystem was originally created are used again. (With the
551 option added, of course!)
553 .BI \-N " number-of-inodes"
554 Overrides the default calculation of the number of inodes that should be
555 reserved for the filesystem (which is based on the number of blocks and
558 ratio). This allows the user to specify the number
559 of desired inodes directly.
561 .BI \-o " creator-os"
562 Overrides the default value of the "creator operating system" field of the
563 filesystem. The creator field is set by default to the name of the OS the
565 executable was compiled for.
567 .B "\-O \fR[^]\fIfeature\fR[,...]"
568 Create a filesystem with the given features (filesystem options),
569 overriding the default filesystem options. The features that are
570 enabled by default are specified by the
572 relation, either in the
579 subsections for the usage types as specified by the
581 option, further modified by the
583 relation found in the
585 subsections for the filesystem and usage types. See the
587 manual page for more details.
588 The filesystem type-specific configuration setting found in the
590 section will override the global default found in
593 The filesystem feature set will be further edited
594 using either the feature set specified by this option,
595 or if this option is not given, by the
597 relation for the filesystem type being created, or in the
599 section of the configuration file.
601 The filesystem feature set is comprised of a list of features, separated
602 by commas, that are to be enabled. To disable a feature, simply
603 prefix the feature name with a caret ('^') character.
604 Features with dependencies will not be removed successfully.
605 The pseudo-filesystem feature "none" will clear all filesystem features.
607 For more information about the features which can be set, please see
612 Quiet execution. Useful if
617 Set the filesystem revision for the new filesystem. Note that 1.2
618 kernels only support revision 0 filesystems. The default is to
619 create revision 1 filesystems.
622 Write superblock and group descriptors only. This is useful if all of
623 the superblock and backup superblocks are corrupted, and a last-ditch
624 recovery method is desired. It causes
627 superblock and group descriptors, while not touching the inode table
628 and the block and inode bitmaps. The
630 program should be run immediately after this option is used, and there
631 is no guarantee that any data will be salvageable. It is critical to
632 specify the correct filesystem blocksize when using this option,
633 or there is no chance of recovery.
636 .\" Check the device for bad blocks before creating the file system
637 .\" using the specified test.
640 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
642 If this option is not specified,
644 will pick a default either via how
645 the command was run (for example, using a name of the form mkfs.ext2,
646 mkfs.ext3, etc.) or via a default as defined by the
648 file. This option controls which filesystem options are used by
649 default, based on the
651 configuration stanza in
652 .BR /etc/mke2fs.conf .
656 option is used to explicitly add or remove filesystem options that
657 should be set in the newly created filesystem, the
658 resulting filesystem may not be supported by the requested
660 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
661 filesystem that is not supported by the ext3 implementation as found in
662 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
663 will create a filesystem that does not have a journal and hence will not
664 be supported by the ext3 filesystem code in the Linux kernel.)
666 .BI \-T " usage-type[,...]"
667 Specify how the filesystem is going to be used, so that
669 can choose optimal filesystem parameters for that use. The usage
670 types that are supported are defined in the configuration file
671 .BR /etc/mke2fs.conf .
672 The user may specify one or more usage types
673 using a comma separated list.
675 If this option is is not specified,
677 will pick a single default usage type based on the size of the filesystem to
678 be created. If the filesystem size is less than 3 megabytes,
680 will use the filesystem type
682 If the filesystem size is greater than or equal to 3 but less than
685 will use the filesystem type
687 If the filesystem size is greater than or equal to 4 terabytes but less than
690 will use the filesystem type
692 If the filesystem size is greater than or equal to 16 terabytes,
694 will use the filesystem type
698 will use the default filesystem type
702 Create the filesystem with the specified UUID.
708 Print the version number of
714 If set to non-zero integer value, its value is used to determine how often
716 is called during inode table initialization.
719 Determines the location of the configuration file (see
720 .BR mke2fs.conf (5)).
722 .BI MKE2FS_FIRST_META_BG
723 If set to non-zero integer value, its value is used to determine first meta
724 block group. This is mostly for debugging purposes.
726 .BI MKE2FS_DEVICE_SECTSIZE
727 If set to non-zero integer value, its value is used to determine physical
731 .BI MKE2FS_SKIP_CHECK_MSG
732 If set, do not show the message of filesystem automatic check caused by
733 mount count or check interval.
737 has been written by Theodore Ts'o <tytso@mit.edu>.
742 option but currently ignores it because the second
743 extended file system does not support fragments yet.
745 There may be other ones. Please, report them to the author.
748 is part of the e2fsprogs package and is available from
749 http://e2fsprogs.sourceforge.net.