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
56 .I reserved-blocks-percentage
89 .I last-mounted-directory
114 @JDEV@.B "mke2fs \-O journal_dev"
119 .\" No external-journal specific journal options yet (size is ignored)
122 .\" @JDEV@.I journal-options
126 @JDEV@.I volume-label
137 @JDEV@.I external-journal
139 @JDEV@.I blocks-count
143 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
146 is the special file corresponding to the device (e.g
149 is the number of blocks on the device. If omitted,
151 automagically figures the file system size. If called as
153 a journal is created as if the
155 option was specified.
157 The defaults of the parameters for the newly created filesystem, if not
158 overridden by the options listed below, are controlled by the
160 configuration file. See the
162 manual page for more details.
165 .BI \-b " block-size"
166 Specify the size of blocks in bytes. Valid block-size values are 1024,
167 2048 and 4096 bytes per block. If omitted,
168 block-size is heuristically determined by the filesystem size and
169 the expected usage of the filesystem (see the
173 is preceded by a negative sign ('-'), then
175 will use heuristics to determine the
176 appropriate block size, with the constraint that the block size will be
179 bytes. This is useful for certain hardware devices which require that
180 the blocksize be a multiple of 2k.
183 Check the device for bad blocks before creating the file system. If
184 this option is specified twice, then a slower read-write
185 test is used instead of a fast read-only test.
187 .BI \-E " extended-options"
188 Set extended options for the filesystem. Extended options are comma
189 separated, and may take an argument using the equals ('=') sign. The
193 in earlier versions of
197 option is still accepted for backwards compatibility. The
198 following extended options are supported:
201 .BI mmp_update_interval= interval
202 Adjust the initial MMP update interval to
204 seconds. Specifying an
206 of 0 means to use the default interval. The specified interval must
207 be less than 300 seconds. Requires that the
211 .BI stride= stride-size
212 Configure the filesystem for a RAID array with
214 filesystem blocks. This is the number of blocks read or written to disk
215 before moving to the next disk, which is sometimes referred to as the
217 This mostly affects placement of filesystem metadata like bitmaps at
219 time to avoid placing them on a single disk, which can hurt performance.
220 It may also be used by the block allocator.
222 .BI stripe_width= stripe-width
223 Configure the filesystem for a RAID array with
225 filesystem blocks per stripe. This is typically stride-size * N, where
226 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
227 parity disk, so N will be the number of disks in the array minus 1).
228 This allows the block allocator to prevent read-modify-write of the
229 parity in a RAID stripe if possible when the data is written.
231 .BI resize= max-online-resize
232 Reserve enough space so that the block group descriptor table can grow
233 to support a filesystem that has
237 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
238 If enabled and the uninit_bg feature is enabled, the inode table will
239 not be fully initialized by
241 This speeds up filesystem
242 initialization noticeably, but it requires the kernel to finish
243 initializing the filesystem in the background when the filesystem is
244 first mounted. If the option value is omitted, it defaults to 1 to
245 enable lazy inode table zeroing.
247 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
248 If enabled, the journal inode will not be fully zeroed out by
250 This speeds up filesystem initialization noticeably, but carries some
251 small risk if the system crashes before the journal has been overwritten
252 entirely one time. If the option value is omitted, it defaults to 1 to
253 enable lazy journal inode zeroing.
256 Set a flag in the filesystem superblock indicating that it may be
257 mounted using experimental kernel code, such as the ext4dev filesystem.
260 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
261 on solid state devices and sparse / thin-provisioned storage). When the device
262 advertises that discard also zeroes data (any subsequent read after the discard
263 and before write returns zero), then mark all not-yet-zeroed inode tables as
264 zeroed. This significantly speeds up filesystem initialization. This is set
268 Do not attempt to discard blocks at mkfs time.
271 .BI \-f " fragment-size"
272 Specify the size of fragments in bytes.
277 to create a filesystem, even if the specified device is not a partition
278 on a block special device, or if other parameters do not make sense.
281 to create a filesystem even if the filesystem appears to be in use
282 or is mounted (a truly dangerous thing to do), this option must be
285 .BI \-g " blocks-per-group"
286 Specify the number of blocks in a block group. There is generally no
287 reason for the user to ever set this parameter, as the default is optimal
288 for the filesystem. (For administrators who are creating
289 filesystems on RAID arrays, it is preferable to use the
291 RAID parameter as part of the
293 option rather than manipulating the number of blocks per group.)
294 This option is generally used by developers who
295 are developing test cases.
297 .BI \-G " number-of-groups"
298 Specify the number of block groups that will be packed together to
299 create a larger virtual block group (or "flex_bg group") in an
300 ext4 filesystem. This improves meta-data locality and performance
301 on meta-data heavy workloads. The number of groups must be a power
302 of 2 and may only be specified if the
304 filesystem feature is enabled.
306 .BI \-i " bytes-per-inode"
307 Specify the bytes/inode ratio.
309 creates an inode for every
311 bytes of space on the disk. The larger the
313 ratio, the fewer inodes will be created. This value generally shouldn't
314 be smaller than the blocksize of the filesystem, since in that case more
315 inodes would be made than can ever be used. Be warned that it is not
316 possible to expand the number
317 of inodes on a filesystem after it is created, so be careful deciding the
318 correct value for this parameter.
320 .BI \-I " inode-size"
321 Specify the size of each inode in bytes.
323 creates 256-byte inodes by default. In kernels after 2.6.10 and some
324 earlier vendor kernels it is possible to utilize inodes larger than
326 extended attributes for improved performance. The
328 value must be a power of 2 larger or equal to 128. The larger the
330 the more space the inode table will consume, and this reduces the usable
331 space in the filesystem and can also negatively impact performance.
333 stored in large inodes are not visible with older kernels, and such
334 filesystems will not be mountable with 2.4 kernels at all. It is not
335 possible to change this value after the filesystem is created.
338 Create the filesystem with an ext3 journal. If the
340 option is not specified, the default journal parameters will be used to
341 create an appropriately sized journal (given the size of the filesystem)
342 stored within the filesystem. Note that you must be using a kernel
343 which has ext3 support in order to actually make use of the journal.
345 .BI \-J " journal-options"
346 Create the ext3 journal using options specified on the command-line.
347 Journal options are comma
348 separated, and may take an argument using the equals ('=') sign.
349 The following journal options are supported:
352 .BI size= journal-size
353 Create an internal journal (i.e., stored inside the filesystem) of size
356 The size of the journal must be at least 1024 filesystem blocks
357 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
358 and may be no more than 10,240,000 filesystem blocks or half the total
359 file system size (whichever is smaller)
361 @JDEV@.BI device= external-journal
362 @JDEV@Attach the filesystem to the journal block device located on
363 @JDEV@.IR external-journal .
365 @JDEV@journal must already have been created using the command
367 @JDEV@.B mke2fs -O journal_dev
368 @JDEV@.I external-journal
371 @JDEV@.I external-journal
372 @JDEV@must have been created with the
373 @JDEV@same block size as the new filesystem.
374 @JDEV@In addition, while there is support for attaching
375 @JDEV@multiple filesystems to a single external journal,
376 @JDEV@the Linux kernel and
378 @JDEV@do not currently support shared external journals yet.
380 @JDEV@Instead of specifying a device name directly,
381 @JDEV@.I external-journal
382 @JDEV@can also be specified by either
383 @JDEV@.BI LABEL= label
386 @JDEV@to locate the external journal by either the volume label or UUID
387 @JDEV@stored in the ext2 superblock at the start of the journal. Use
388 @JDEV@.BR dumpe2fs (8)
389 @JDEV@to display a journal device's volume label and UUID. See also the
392 @JDEV@.BR tune2fs (8).
395 @JDEV@Only one of the
396 @JDEV@.BR size " or " device
397 @JDEV@options can be given for a filesystem.
400 Read the bad blocks list from
402 Note that the block numbers in the bad block list must be generated
403 using the same block size as used by
409 is a much simpler and less error-prone method of checking a disk for bad
410 blocks before formatting it, as
412 will automatically pass the correct parameters to the
416 .BI \-L " new-volume-label"
417 Set the volume label for the filesystem to
418 .IR new-volume-label .
419 The maximum length of the
420 volume label is 16 bytes.
422 .BI \-m " reserved-blocks-percentage"
423 Specify the percentage of the filesystem blocks reserved for
424 the super-user. This avoids fragmentation, and allows root-owned
427 to continue to function correctly after non-privileged processes are
428 prevented from writing to the filesystem. The default percentage
431 .BI \-M " last-mounted-directory"
432 Set the last mounted directory for the filesystem. This might be useful
433 for the sake of utilities that key off of the last mounted directory to
434 determine where the filesystem should be mounted.
439 to not actually create a filesystem, but display what it
440 would do if it were to create a filesystem. This can be used to
441 determine the location of the backup superblocks for a particular
442 filesystem, so long as the
444 parameters that were passed when the
445 filesystem was originally created are used again. (With the
447 option added, of course!)
449 .BI \-N " number-of-inodes"
450 Overrides the default calculation of the number of inodes that should be
451 reserved for the filesystem (which is based on the number of blocks and
454 ratio). This allows the user to specify the number
455 of desired inodes directly.
457 .BI \-o " creator-os"
458 Overrides the default value of the "creator operating system" field of the
459 filesystem. The creator field is set by default to the name of the OS the
461 executable was compiled for.
463 .B "\-O \fIfeature\fR[,...]"
464 Create a filesystem with the given features (filesystem options),
465 overriding the default filesystem options. The features that are
466 enabled by default are specified by the
468 relation, either in the
475 subsections for the usage types as specified by the
477 option, further modified by the
479 relation found in the
481 subsections for the filesystem and usage types. See the
483 manual page for more details.
484 The filesystem type-specific configuration setting found in the
486 section will override the global default found in
489 The filesystem feature set will be further edited
490 using either the feature set specified by this option,
491 or if this option is not given, by the
493 relation for the filesystem type being created, or in the
495 section of the configuration file.
497 The filesystem feature set is comprised of a list of features, separated
498 by commas, that are to be enabled. To disable a feature, simply
499 prefix the feature name with a caret ('^') character. The
500 pseudo-filesystem feature "none" will clear all filesystem features.
504 Use hashed b-trees to speed up lookups in large directories.
507 Instead of using the indirect block scheme for storing the location of
508 data blocks in an inode, use extents instead. This is a much more
509 efficient encoding which speeds up filesystem access, especially for
513 Store file type information in directory entries.
516 Allow the per-block group metadata (allocation bitmaps and inode tables)
517 to be placed anywhere on the storage media. In addition,
519 will place the per-block group metadata together starting at the first
520 block group of each "flex_bg group". The size of the flex_bg group
521 can be specified using the
526 Create an ext3 journal (as if using the
531 @JDEV@Create an external ext3 journal on the given device
532 @JDEV@instead of a regular ext2 filesystem.
534 @JDEV@.I external-journal
535 @JDEV@must be created with the same
536 @JDEV@block size as the filesystems that will be using it.
539 Filesystem can contain files that are greater than 2GB. (Modern kernels
540 set this feature automatically when a file > 2GB is created.)
543 Create quota inodes (inode# 3 for userquota and inode# 4 for group quota) and
544 set them in the superblock. With this feature, the quotas will be enabled
545 automatically when the filesystem is mounted.
548 Reserve space so the block group descriptor table may grow in the future.
549 Useful for online resizing using
553 will attempt to reserve enough space so that the
554 filesystem may grow to 1024 times its initial size. This can be changed
560 Create a filesystem with fewer superblock backup copies
561 (saves space on large filesystems).
564 Create a filesystem without initializing all of the block groups. This
565 feature also enables checksums and highest-inode-used statistics in each
566 blockgroup. This feature can
567 speed up filesystem creation time noticeably (if lazy_itable_init is
568 enabled), and can also reduce
570 time dramatically. It is only supported by the ext4 filesystem in
571 recent Linux kernels.
575 Quiet execution. Useful if
580 Set the filesystem revision for the new filesystem. Note that 1.2
581 kernels only support revision 0 filesystems. The default is to
582 create revision 1 filesystems.
585 Write superblock and group descriptors only. This is useful if all of
586 the superblock and backup superblocks are corrupted, and a last-ditch
587 recovery method is desired. It causes
590 superblock and group descriptors, while not touching the inode table
591 and the block and inode bitmaps. The
593 program should be run immediately after this option is used, and there
594 is no guarantee that any data will be salvageable. It is critical to
595 specify the correct filesystem blocksize when using this option,
596 or there is no chance of recovery.
599 .\" Check the device for bad blocks before creating the file system
600 .\" using the specified test.
603 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is to be created.
604 If this option is not specified,
606 will pick a default either via how
607 the command was run (for example, using a name of the form mkfs.ext2,
608 mkfs.ext3, etc.) or via a default as defined by the
609 .BR /etc/mke2fs.conf (5)
610 file. This option controls which filesystem options are used by
611 default, based on the
613 configuration stanza in
614 .BR /etc/mke2fs.conf (5).
618 option is used to explicitly add or remove filesystem options that
619 should be set in the newly created filesystem, the
620 resulting filesystem may not be supported by the requested
622 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
623 filesystem that is not supported by the ext3 implementation as found in
624 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
625 will create a filesystem that does not have a journal and hence will not
626 be supported by the ext3 filesystem code in the Linux kernel.)
628 .BI \-T " usage-type[,...]"
629 Specify how the filesystem is going to be used, so that
631 can choose optimal filesystem parameters for that use. The usage
632 types that are supported are defined in the configuration file
633 .BR /etc/mke2fs.conf (5).
634 The user may specify one or more usage types
635 using a comma separated list.
637 If this option is is not specified,
639 will pick a single default usage type based on the size of the filesystem to
640 be created. If the filesystem size is less than or equal to 3 megabytes,
642 will use the filesystem type
644 If the filesystem size is greater than 3 but less than or equal to
647 will use the filesystem type
649 If the filesystem size is greater than or equal to 4 terabytes but less than
652 will use the filesystem type
654 If the filesystem size is greater than or equal to 16 terabytes,
656 will use the filesystem type
660 will use the default filesystem type
664 Create the filesystem with the specified UUID.
670 Print the version number of
676 If set to non-zero integer value, its value is used to determine how often
678 is called during inode table initialization.
681 Determines the location of the configuration file (see
682 .BR mke2fs.conf (5)).
684 .BI MKE2FS_FIRST_META_BG
685 If set to non-zero integer value, its value is used to determine first meta
686 block group. This is mostly for debugging purposes.
688 .BI MKE2FS_DEVICE_SECTSIZE
689 If set to non-zero integer value, its value is used to determine physical
693 .BI MKE2FS_SKIP_CHECK_MSG
694 If set, do not show the message of filesystem automatic check caused by
695 mount count or check interval.
699 has been written by Theodore Ts'o <tytso@mit.edu>.
704 option but currently ignores it because the second
705 extended file system does not support fragments yet.
707 There may be other ones. Please, report them to the author.
710 is part of the e2fsprogs package and is available from
711 http://e2fsprogs.sourceforge.net.