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
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. By default (if bigalloc is enabled and no cluster size is
194 otherwise specified using this option), the cluster size will be 16
195 times the block size.
198 Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
199 lot of buffer cache memory, which may impact other applications running
200 on a busy server. This option will cause mke2fs to run much more
201 slowly, however, so there is a tradeoff to using direct I/O.
203 .BI \-E " extended-options"
204 Set extended options for the filesystem. Extended options are comma
205 separated, and may take an argument using the equals ('=') sign. The
209 in earlier versions of
213 option is still accepted for backwards compatibility, but is deprecated.
214 The following extended options are supported:
217 .BI mmp_update_interval= interval
218 Adjust the initial MMP update interval to
220 seconds. Specifying an
222 of 0 means to use the default interval. The specified interval must
223 be less than 300 seconds. Requires that the
227 .BI stride= stride-size
228 Configure the filesystem for a RAID array with
230 filesystem blocks. This is the number of blocks read or written to disk
231 before moving to the next disk, which is sometimes referred to as the
233 This mostly affects placement of filesystem metadata like bitmaps at
235 time to avoid placing them on a single disk, which can hurt performance.
236 It may also be used by the block allocator.
238 .BI stripe_width= stripe-width
239 Configure the filesystem for a RAID array with
241 filesystem blocks per stripe. This is typically stride-size * N, where
242 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
243 parity disk, so N will be the number of disks in the array minus 1).
244 This allows the block allocator to prevent read-modify-write of the
245 parity in a RAID stripe if possible when the data is written.
247 .BI resize= max-online-resize
248 Reserve enough space so that the block group descriptor table can grow
249 to support a filesystem that has
253 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
254 If enabled and the uninit_bg feature is enabled, the inode table will
255 not be fully initialized by
257 This speeds up filesystem
258 initialization noticeably, but it requires the kernel to finish
259 initializing the filesystem in the background when the filesystem is
260 first mounted. If the option value is omitted, it defaults to 1 to
261 enable lazy inode table zeroing.
263 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
264 If enabled, the journal inode will not be fully zeroed out by
266 This speeds up filesystem initialization noticeably, but carries some
267 small risk if the system crashes before the journal has been overwritten
268 entirely one time. If the option value is omitted, it defaults to 1 to
269 enable lazy journal inode zeroing.
271 .BI root_owner [=uid:gid]
272 Specify the numeric user and group ID of the root directory. If no UID:GID
273 is specified, use the user and group ID of the user running \fBmke2fs\fR.
274 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
275 set by default to the UID and GID of the user running the mke2fs command.
276 The \fBroot_owner=\fR option allows explicitly specifying these values,
277 and avoid side-effects for users that do not expect the contents of the
278 filesystem to change based on the user running \fBmke2fs\fR.
281 Set a flag in the filesystem superblock indicating that it may be
282 mounted using experimental kernel code, such as the ext4dev filesystem.
285 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
286 on solid state devices and sparse / thin-provisioned storage). When the device
287 advertises that discard also zeroes data (any subsequent read after the discard
288 and before write returns zero), then mark all not-yet-zeroed inode tables as
289 zeroed. This significantly speeds up filesystem initialization. This is set
293 Do not attempt to discard blocks at mkfs time.
294 @QUOTA_MAN_COMMENT@.TP
295 @QUOTA_MAN_COMMENT@.BI quotatype
296 @QUOTA_MAN_COMMENT@Specify which quota type ('usr' or 'grp') is to be
297 @QUOTA_MAN_COMMENT@initialized. This option has effect only if the
298 @QUOTA_MAN_COMMENT@.B quota
299 @QUOTA_MAN_COMMENT@feature is set. Without this extended option, the default
300 @QUOTA_MAN_COMMENT@behavior is to initialize both user and group quotas.
303 .BI \-f " fragment-size"
304 Specify the size of fragments in bytes.
309 to create a filesystem, even if the specified device is not a partition
310 on a block special device, or if other parameters do not make sense.
313 to create a filesystem even if the filesystem appears to be in use
314 or is mounted (a truly dangerous thing to do), this option must be
317 .BI \-g " blocks-per-group"
318 Specify the number of blocks in a block group. There is generally no
319 reason for the user to ever set this parameter, as the default is optimal
320 for the filesystem. (For administrators who are creating
321 filesystems on RAID arrays, it is preferable to use the
323 RAID parameter as part of the
325 option rather than manipulating the number of blocks per group.)
326 This option is generally used by developers who
327 are developing test cases.
329 If the bigalloc feature is enabled, the
331 option will specify the number of clusters in a block group.
333 .BI \-G " number-of-groups"
334 Specify the number of block groups that will be packed together to
335 create a larger virtual block group (or "flex_bg group") in an
336 ext4 filesystem. This improves meta-data locality and performance
337 on meta-data heavy workloads. The number of groups must be a power
338 of 2 and may only be specified if the
340 filesystem feature is enabled.
342 .BI \-i " bytes-per-inode"
343 Specify the bytes/inode ratio.
345 creates an inode for every
347 bytes of space on the disk. The larger the
349 ratio, the fewer inodes will be created. This value generally shouldn't
350 be smaller than the blocksize of the filesystem, since in that case more
351 inodes would be made than can ever be used. Be warned that it is not
352 possible to change this ratio on a filesystem after it is created, so be
353 careful deciding the correct value for this parameter. Note that resizing
354 a filesystem changes the numer of inodes to maintain this ratio.
356 .BI \-I " inode-size"
357 Specify the size of each inode in bytes.
359 creates 256-byte inodes by default. In kernels after 2.6.10 and some
360 earlier vendor kernels it is possible to utilize inodes larger than
362 extended attributes for improved performance. The
364 value must be a power of 2 larger or equal to 128. The larger the
366 the more space the inode table will consume, and this reduces the usable
367 space in the filesystem and can also negatively impact performance.
369 stored in large inodes are not visible with older kernels, and such
370 filesystems will not be mountable with 2.4 kernels at all. It is not
371 possible to change this value after the filesystem is created.
374 Create the filesystem with an ext3 journal. If the
376 option is not specified, the default journal parameters will be used to
377 create an appropriately sized journal (given the size of the filesystem)
378 stored within the filesystem. Note that you must be using a kernel
379 which has ext3 support in order to actually make use of the journal.
381 .BI \-J " journal-options"
382 Create the ext3 journal using options specified on the command-line.
383 Journal options are comma
384 separated, and may take an argument using the equals ('=') sign.
385 The following journal options are supported:
388 .BI size= journal-size
389 Create an internal journal (i.e., stored inside the filesystem) of size
392 The size of the journal must be at least 1024 filesystem blocks
393 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
394 and may be no more than 10,240,000 filesystem blocks or half the total
395 file system size (whichever is smaller)
397 @JDEV@.BI device= external-journal
398 @JDEV@Attach the filesystem to the journal block device located on
399 @JDEV@.IR external-journal .
401 @JDEV@journal must already have been created using the command
403 @JDEV@.B mke2fs -O journal_dev
404 @JDEV@.I external-journal
407 @JDEV@.I external-journal
408 @JDEV@must have been created with the
409 @JDEV@same block size as the new filesystem.
410 @JDEV@In addition, while there is support for attaching
411 @JDEV@multiple filesystems to a single external journal,
412 @JDEV@the Linux kernel and
414 @JDEV@do not currently support shared external journals yet.
416 @JDEV@Instead of specifying a device name directly,
417 @JDEV@.I external-journal
418 @JDEV@can also be specified by either
419 @JDEV@.BI LABEL= label
422 @JDEV@to locate the external journal by either the volume label or UUID
423 @JDEV@stored in the ext2 superblock at the start of the journal. Use
424 @JDEV@.BR dumpe2fs (8)
425 @JDEV@to display a journal device's volume label and UUID. See also the
428 @JDEV@.BR tune2fs (8).
431 @JDEV@Only one of the
432 @JDEV@.BR size " or " device
433 @JDEV@options can be given for a filesystem.
436 Read the bad blocks list from
438 Note that the block numbers in the bad block list must be generated
439 using the same block size as used by
445 is a much simpler and less error-prone method of checking a disk for bad
446 blocks before formatting it, as
448 will automatically pass the correct parameters to the
452 .BI \-L " new-volume-label"
453 Set the volume label for the filesystem to
454 .IR new-volume-label .
455 The maximum length of the
456 volume label is 16 bytes.
458 .BI \-m " reserved-blocks-percentage"
459 Specify the percentage of the filesystem blocks reserved for
460 the super-user. This avoids fragmentation, and allows root-owned
463 to continue to function correctly after non-privileged processes are
464 prevented from writing to the filesystem. The default percentage
467 .BI \-M " last-mounted-directory"
468 Set the last mounted directory for the filesystem. This might be useful
469 for the sake of utilities that key off of the last mounted directory to
470 determine where the filesystem should be mounted.
475 to not actually create a filesystem, but display what it
476 would do if it were to create a filesystem. This can be used to
477 determine the location of the backup superblocks for a particular
478 filesystem, so long as the
480 parameters that were passed when the
481 filesystem was originally created are used again. (With the
483 option added, of course!)
485 .BI \-N " number-of-inodes"
486 Overrides the default calculation of the number of inodes that should be
487 reserved for the filesystem (which is based on the number of blocks and
490 ratio). This allows the user to specify the number
491 of desired inodes directly.
493 .BI \-o " creator-os"
494 Overrides the default value of the "creator operating system" field of the
495 filesystem. The creator field is set by default to the name of the OS the
497 executable was compiled for.
499 .B "\-O \fIfeature\fR[,...]"
500 Create a filesystem with the given features (filesystem options),
501 overriding the default filesystem options. The features that are
502 enabled by default are specified by the
504 relation, either in the
511 subsections for the usage types as specified by the
513 option, further modified by the
515 relation found in the
517 subsections for the filesystem and usage types. See the
519 manual page for more details.
520 The filesystem type-specific configuration setting found in the
522 section will override the global default found in
525 The filesystem feature set will be further edited
526 using either the feature set specified by this option,
527 or if this option is not given, by the
529 relation for the filesystem type being created, or in the
531 section of the configuration file.
533 The filesystem feature set is comprised of a list of features, separated
534 by commas, that are to be enabled. To disable a feature, simply
535 prefix the feature name with a caret ('^') or a minus ('-') character.
536 Features with dependencies will not be removed successfully.
537 The pseudo-filesystem feature "none" will clear all filesystem features.
539 For more information about the features which can be set, please see
544 Quiet execution. Useful if
549 Set the filesystem revision for the new filesystem. Note that 1.2
550 kernels only support revision 0 filesystems. The default is to
551 create revision 1 filesystems.
554 Write superblock and group descriptors only. This is useful if all of
555 the superblock and backup superblocks are corrupted, and a last-ditch
556 recovery method is desired. It causes
559 superblock and group descriptors, while not touching the inode table
560 and the block and inode bitmaps. The
562 program should be run immediately after this option is used, and there
563 is no guarantee that any data will be salvageable. It is critical to
564 specify the correct filesystem blocksize when using this option,
565 or there is no chance of recovery.
568 .\" Check the device for bad blocks before creating the file system
569 .\" using the specified test.
572 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
574 If this option is not specified,
576 will pick a default either via how
577 the command was run (for example, using a name of the form mkfs.ext2,
578 mkfs.ext3, etc.) or via a default as defined by the
580 file. This option controls which filesystem options are used by
581 default, based on the
583 configuration stanza in
584 .BR /etc/mke2fs.conf .
588 option is used to explicitly add or remove filesystem options that
589 should be set in the newly created filesystem, the
590 resulting filesystem may not be supported by the requested
592 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
593 filesystem that is not supported by the ext3 implementation as found in
594 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
595 will create a filesystem that does not have a journal and hence will not
596 be supported by the ext3 filesystem code in the Linux kernel.)
598 .BI \-T " usage-type[,...]"
599 Specify how the filesystem is going to be used, so that
601 can choose optimal filesystem parameters for that use. The usage
602 types that are supported are defined in the configuration file
603 .BR /etc/mke2fs.conf .
604 The user may specify one or more usage types
605 using a comma separated list.
607 If this option is is not specified,
609 will pick a single default usage type based on the size of the filesystem to
610 be created. If the filesystem size is less than or equal to 3 megabytes,
612 will use the filesystem type
614 If the filesystem size is greater than 3 but less than or equal to
617 will use the filesystem type
619 If the filesystem size is greater than or equal to 4 terabytes but less than
622 will use the filesystem type
624 If the filesystem size is greater than or equal to 16 terabytes,
626 will use the filesystem type
630 will use the default filesystem type
634 Create the filesystem with the specified UUID.
640 Print the version number of
646 If set to non-zero integer value, its value is used to determine how often
648 is called during inode table initialization.
651 Determines the location of the configuration file (see
652 .BR mke2fs.conf (5)).
654 .BI MKE2FS_FIRST_META_BG
655 If set to non-zero integer value, its value is used to determine first meta
656 block group. This is mostly for debugging purposes.
658 .BI MKE2FS_DEVICE_SECTSIZE
659 If set to non-zero integer value, its value is used to determine physical
663 .BI MKE2FS_SKIP_CHECK_MSG
664 If set, do not show the message of filesystem automatic check caused by
665 mount count or check interval.
669 has been written by Theodore Ts'o <tytso@mit.edu>.
674 option but currently ignores it because the second
675 extended file system does not support fragments yet.
677 There may be other ones. Please, report them to the author.
680 is part of the e2fsprogs package and is available from
681 http://e2fsprogs.sourceforge.net.