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
142 @JDEV@.I blocks-count
146 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
149 is the special file corresponding to the device (e.g
152 is the number of blocks on the device. If omitted,
154 automagically figures the file system size. If called as
156 a journal is created as if the
158 option was specified.
160 The defaults of the parameters for the newly created filesystem, if not
161 overridden by the options listed below, are controlled by the
163 configuration file. See the
165 manual page for more details.
168 .BI \-b " block-size"
169 Specify the size of blocks in bytes. Valid block-size values are 1024,
170 2048 and 4096 bytes per block. If omitted,
171 block-size is heuristically determined by the filesystem size and
172 the expected usage of the filesystem (see the
176 is preceded by a negative sign ('-'), then
178 will use heuristics to determine the
179 appropriate block size, with the constraint that the block size will be
182 bytes. This is useful for certain hardware devices which require that
183 the blocksize be a multiple of 2k.
186 Check the device for bad blocks before creating the file system. If
187 this option is specified twice, then a slower read-write
188 test is used instead of a fast read-only test.
190 .B \-C " cluster-size"
191 Specify the size of cluster in bytes for filesystems using the bigalloc
192 feature. Valid cluster-size values are from 2048 to 256M bytes per
193 cluster. This can only be specified if the bigalloc feature is
196 man page for more details about bigalloc.) The default cluster size if
197 bigalloc is enabled is 16 times the block size.
200 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
201 lot of buffer cache memory, which may impact other applications running
202 on a busy server. This option will cause mke2fs to run much more
203 slowly, however, so there is a tradeoff to using direct I/O.
205 .BI \-E " extended-options"
206 Set extended options for the filesystem. Extended options are comma
207 separated, and may take an argument using the equals ('=') sign. The
211 in earlier versions of
215 option is still accepted for backwards compatibility, but is deprecated.
216 The following extended options are supported:
219 .BI mmp_update_interval= interval
220 Adjust the initial MMP update interval to
222 seconds. Specifying an
224 of 0 means to use the default interval. The specified interval must
225 be less than 300 seconds. Requires that the
229 .BI stride= stride-size
230 Configure the filesystem for a RAID array with
232 filesystem blocks. This is the number of blocks read or written to disk
233 before moving to the next disk, which is sometimes referred to as the
235 This mostly affects placement of filesystem metadata like bitmaps at
237 time to avoid placing them on a single disk, which can hurt performance.
238 It may also be used by the block allocator.
240 .BI stripe_width= stripe-width
241 Configure the filesystem for a RAID array with
243 filesystem blocks per stripe. This is typically stride-size * N, where
244 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
245 parity disk, so N will be the number of disks in the array minus 1).
246 This allows the block allocator to prevent read-modify-write of the
247 parity in a RAID stripe if possible when the data is written.
250 Create the filesystem at an offset from the beginning of the device or
251 file. This can be useful when creating disk images for virtual machines.
253 .BI resize= max-online-resize
254 Reserve enough space so that the block group descriptor table can grow
255 to support a filesystem that has
259 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
260 If enabled and the uninit_bg feature is enabled, the inode table will
261 not be fully initialized by
263 This speeds up filesystem
264 initialization noticeably, but it requires the kernel to finish
265 initializing the filesystem in the background when the filesystem is
266 first mounted. If the option value is omitted, it defaults to 1 to
267 enable lazy inode table zeroing.
269 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
270 If enabled, the journal inode will not be fully zeroed out by
272 This speeds up filesystem initialization noticeably, but carries some
273 small risk if the system crashes before the journal has been overwritten
274 entirely one time. If the option value is omitted, it defaults to 1 to
275 enable lazy journal inode zeroing.
277 .BI num_backup_sb= <0|1|2>
280 file system feature is enabled this option controls whether there will
281 be 0, 1, or 2 backup superblocks created in the file system.
283 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
284 Place the allocation bitmaps and the inode table at the beginning of the
285 disk. This option requires that the flex_bg file system feature to be
286 enabled in order for it to have effect, and will also create the journal
287 at the beginning of the file system. This option is useful for flash
288 devices that use SLC flash at the beginning of the disk.
289 It also maximizes the range of contiguous data blocks, which
290 can be useful for certain specialized use cases, such as supported
293 .BI root_owner [=uid:gid]
294 Specify the numeric user and group ID of the root directory. If no UID:GID
295 is specified, use the user and group ID of the user running \fBmke2fs\fR.
296 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
297 set by default to the UID and GID of the user running the mke2fs command.
298 The \fBroot_owner=\fR option allows explicitly specifying these values,
299 and avoid side-effects for users that do not expect the contents of the
300 filesystem to change based on the user running \fBmke2fs\fR.
303 Set a flag in the filesystem superblock indicating that it may be
304 mounted using experimental kernel code, such as the ext4dev filesystem.
307 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
308 on solid state devices and sparse / thin-provisioned storage). When the device
309 advertises that discard also zeroes data (any subsequent read after the discard
310 and before write returns zero), then mark all not-yet-zeroed inode tables as
311 zeroed. This significantly speeds up filesystem initialization. This is set
315 Do not attempt to discard blocks at mkfs time.
316 @QUOTA_MAN_COMMENT@.TP
317 @QUOTA_MAN_COMMENT@.BI quotatype
318 @QUOTA_MAN_COMMENT@Specify which quota type ('usr' or 'grp') is to be
319 @QUOTA_MAN_COMMENT@initialized. This option has effect only if the
320 @QUOTA_MAN_COMMENT@.B quota
321 @QUOTA_MAN_COMMENT@feature is set. Without this extended option, the default
322 @QUOTA_MAN_COMMENT@behavior is to initialize both user and group quotas.
325 .BI \-f " fragment-size"
326 Specify the size of fragments in bytes.
331 to create a filesystem, even if the specified device is not a partition
332 on a block special device, or if other parameters do not make sense.
335 to create a filesystem even if the filesystem appears to be in use
336 or is mounted (a truly dangerous thing to do), this option must be
339 .BI \-g " blocks-per-group"
340 Specify the number of blocks in a block group. There is generally no
341 reason for the user to ever set this parameter, as the default is optimal
342 for the filesystem. (For administrators who are creating
343 filesystems on RAID arrays, it is preferable to use the
345 RAID parameter as part of the
347 option rather than manipulating the number of blocks per group.)
348 This option is generally used by developers who
349 are developing test cases.
351 If the bigalloc feature is enabled, the
353 option will specify the number of clusters in a block group.
355 .BI \-G " number-of-groups"
356 Specify the number of block groups that will be packed together to
357 create a larger virtual block group (or "flex_bg group") in an
358 ext4 filesystem. This improves meta-data locality and performance
359 on meta-data heavy workloads. The number of groups must be a power
360 of 2 and may only be specified if the
362 filesystem feature is enabled.
364 .BI \-i " bytes-per-inode"
365 Specify the bytes/inode ratio.
367 creates an inode for every
369 bytes of space on the disk. The larger the
371 ratio, the fewer inodes will be created. This value generally shouldn't
372 be smaller than the blocksize of the filesystem, since in that case more
373 inodes would be made than can ever be used. Be warned that it is not
374 possible to change this ratio on a filesystem after it is created, so be
375 careful deciding the correct value for this parameter. Note that resizing
376 a filesystem changes the numer of inodes to maintain this ratio.
378 .BI \-I " inode-size"
379 Specify the size of each inode in bytes.
382 value must be a power of 2 larger or equal to 128. The larger the
384 the more space the inode table will consume, and this reduces the usable
385 space in the filesystem and can also negatively impact performance.
387 possible to change this value after the filesystem is created.
389 In kernels after 2.6.10 and some
390 earlier vendor kernels it is possible to utilize inodes larger than
392 extended attributes for improved performance.
394 stored in large inodes are not visible with older kernels, and such
395 filesystems will not be mountable with 2.4 kernels at all.
397 The default inode size is controlled by the
401 file shipped with e2fsprogs, the default inode size is 256 bytes for
402 most file systems, except for small file systems where the inode size
406 Create the filesystem with an ext3 journal. If the
408 option is not specified, the default journal parameters will be used to
409 create an appropriately sized journal (given the size of the filesystem)
410 stored within the filesystem. Note that you must be using a kernel
411 which has ext3 support in order to actually make use of the journal.
413 .BI \-J " journal-options"
414 Create the ext3 journal using options specified on the command-line.
415 Journal options are comma
416 separated, and may take an argument using the equals ('=') sign.
417 The following journal options are supported:
420 .BI size= journal-size
421 Create an internal journal (i.e., stored inside the filesystem) of size
424 The size of the journal must be at least 1024 filesystem blocks
425 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
426 and may be no more than 10,240,000 filesystem blocks or half the total
427 file system size (whichever is smaller)
429 .BI location =journal-location
430 Specify the location of the journal. The argument
432 can either be specified as a block number, or if the number has a units
433 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
434 beginning of the file system.
436 @JDEV@.BI device= external-journal
437 @JDEV@Attach the filesystem to the journal block device located on
438 @JDEV@.IR external-journal .
440 @JDEV@journal must already have been created using the command
442 @JDEV@.B mke2fs -O journal_dev
443 @JDEV@.I external-journal
446 @JDEV@.I external-journal
447 @JDEV@must have been created with the
448 @JDEV@same block size as the new filesystem.
449 @JDEV@In addition, while there is support for attaching
450 @JDEV@multiple filesystems to a single external journal,
451 @JDEV@the Linux kernel and
453 @JDEV@do not currently support shared external journals yet.
455 @JDEV@Instead of specifying a device name directly,
456 @JDEV@.I external-journal
457 @JDEV@can also be specified by either
458 @JDEV@.BI LABEL= label
461 @JDEV@to locate the external journal by either the volume label or UUID
462 @JDEV@stored in the ext2 superblock at the start of the journal. Use
463 @JDEV@.BR dumpe2fs (8)
464 @JDEV@to display a journal device's volume label and UUID. See also the
467 @JDEV@.BR tune2fs (8).
470 @JDEV@Only one of the
471 @JDEV@.BR size " or " device
472 @JDEV@options can be given for a filesystem.
475 Read the bad blocks list from
477 Note that the block numbers in the bad block list must be generated
478 using the same block size as used by
484 is a much simpler and less error-prone method of checking a disk for bad
485 blocks before formatting it, as
487 will automatically pass the correct parameters to the
491 .BI \-L " new-volume-label"
492 Set the volume label for the filesystem to
493 .IR new-volume-label .
494 The maximum length of the
495 volume label is 16 bytes.
497 .BI \-m " reserved-blocks-percentage"
498 Specify the percentage of the filesystem blocks reserved for
499 the super-user. This avoids fragmentation, and allows root-owned
502 to continue to function correctly after non-privileged processes are
503 prevented from writing to the filesystem. The default percentage
506 .BI \-M " last-mounted-directory"
507 Set the last mounted directory for the filesystem. This might be useful
508 for the sake of utilities that key off of the last mounted directory to
509 determine where the filesystem should be mounted.
514 to not actually create a filesystem, but display what it
515 would do if it were to create a filesystem. This can be used to
516 determine the location of the backup superblocks for a particular
517 filesystem, so long as the
519 parameters that were passed when the
520 filesystem was originally created are used again. (With the
522 option added, of course!)
524 .BI \-N " number-of-inodes"
525 Overrides the default calculation of the number of inodes that should be
526 reserved for the filesystem (which is based on the number of blocks and
529 ratio). This allows the user to specify the number
530 of desired inodes directly.
532 .BI \-o " creator-os"
533 Overrides the default value of the "creator operating system" field of the
534 filesystem. The creator field is set by default to the name of the OS the
536 executable was compiled for.
538 .B "\-O \fR[^]\fIfeature\fR[,...]"
539 Create a filesystem with the given features (filesystem options),
540 overriding the default filesystem options. The features that are
541 enabled by default are specified by the
543 relation, either in the
550 subsections for the usage types as specified by the
552 option, further modified by the
554 relation found in the
556 subsections for the filesystem and usage types. See the
558 manual page for more details.
559 The filesystem type-specific configuration setting found in the
561 section will override the global default found in
564 The filesystem feature set will be further edited
565 using either the feature set specified by this option,
566 or if this option is not given, by the
568 relation for the filesystem type being created, or in the
570 section of the configuration file.
572 The filesystem feature set is comprised of a list of features, separated
573 by commas, that are to be enabled. To disable a feature, simply
574 prefix the feature name with a caret ('^') character.
575 Features with dependencies will not be removed successfully.
576 The pseudo-filesystem feature "none" will clear all filesystem features.
578 For more information about the features which can be set, please see
583 Quiet execution. Useful if
588 Set the filesystem revision for the new filesystem. Note that 1.2
589 kernels only support revision 0 filesystems. The default is to
590 create revision 1 filesystems.
593 Write superblock and group descriptors only. This is useful if all of
594 the superblock and backup superblocks are corrupted, and a last-ditch
595 recovery method is desired. It causes
598 superblock and group descriptors, while not touching the inode table
599 and the block and inode bitmaps. The
601 program should be run immediately after this option is used, and there
602 is no guarantee that any data will be salvageable. It is critical to
603 specify the correct filesystem blocksize when using this option,
604 or there is no chance of recovery.
607 .\" Check the device for bad blocks before creating the file system
608 .\" using the specified test.
611 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
613 If this option is not specified,
615 will pick a default either via how
616 the command was run (for example, using a name of the form mkfs.ext2,
617 mkfs.ext3, etc.) or via a default as defined by the
619 file. This option controls which filesystem options are used by
620 default, based on the
622 configuration stanza in
623 .BR /etc/mke2fs.conf .
627 option is used to explicitly add or remove filesystem options that
628 should be set in the newly created filesystem, the
629 resulting filesystem may not be supported by the requested
631 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
632 filesystem that is not supported by the ext3 implementation as found in
633 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
634 will create a filesystem that does not have a journal and hence will not
635 be supported by the ext3 filesystem code in the Linux kernel.)
637 .BI \-T " usage-type[,...]"
638 Specify how the filesystem is going to be used, so that
640 can choose optimal filesystem parameters for that use. The usage
641 types that are supported are defined in the configuration file
642 .BR /etc/mke2fs.conf .
643 The user may specify one or more usage types
644 using a comma separated list.
646 If this option is is not specified,
648 will pick a single default usage type based on the size of the filesystem to
649 be created. If the filesystem size is less than or equal to 3 megabytes,
651 will use the filesystem type
653 If the filesystem size is greater than 3 but less than or equal to
656 will use the filesystem type
658 If the filesystem size is greater than or equal to 4 terabytes but less than
661 will use the filesystem type
663 If the filesystem size is greater than or equal to 16 terabytes,
665 will use the filesystem type
669 will use the default filesystem type
673 Create the filesystem with the specified UUID.
679 Print the version number of
685 If set to non-zero integer value, its value is used to determine how often
687 is called during inode table initialization.
690 Determines the location of the configuration file (see
691 .BR mke2fs.conf (5)).
693 .BI MKE2FS_FIRST_META_BG
694 If set to non-zero integer value, its value is used to determine first meta
695 block group. This is mostly for debugging purposes.
697 .BI MKE2FS_DEVICE_SECTSIZE
698 If set to non-zero integer value, its value is used to determine physical
702 .BI MKE2FS_SKIP_CHECK_MSG
703 If set, do not show the message of filesystem automatic check caused by
704 mount count or check interval.
708 has been written by Theodore Ts'o <tytso@mit.edu>.
713 option but currently ignores it because the second
714 extended file system does not support fragments yet.
716 There may be other ones. Please, report them to the author.
719 is part of the e2fsprogs package and is available from
720 http://e2fsprogs.sourceforge.net.