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 stride= stride-size
202 Configure the filesystem for a RAID array with
204 filesystem blocks. This is the number of blocks read or written to disk
205 before moving to the next disk, which is sometimes referred to as the
207 This mostly affects placement of filesystem metadata like bitmaps at
209 time to avoid placing them on a single disk, which can hurt performance.
210 It may also be used by the block allocator.
212 .BI stripe-width= stripe-width
213 Configure the filesystem for a RAID array with
215 filesystem blocks per stripe. This is typically stride-size * N, where
216 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
217 parity disk, so N will be the number of disks in the array minus 1).
218 This allows the block allocator to prevent read-modify-write of the
219 parity in a RAID stripe if possible when the data is written.
221 .BI resize= max-online-resize
222 Reserve enough space so that the block group descriptor table can grow
223 to support a filesystem that has
227 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
228 If enabled and the uninit_bg feature is enabled, the inode table will
229 not be fully initialized by
231 This speeds up filesystem
232 initialization noticeably, but it requires the kernel to finish
233 initializing the filesystem in the background when the filesystem is
234 first mounted. If the option value is omitted, it defaults to 1 to
235 enable lazy inode table initialization.
238 Set a flag in the filesystem superblock indicating that it may be
239 mounted using experimental kernel code, such as the ext4dev filesystem.
242 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
243 on solid state devices and sparse / thin-provisioned storage). When the device
244 advertises that discard also zeroes data (any subsequent read after the discard
245 and before write returns zero), then mark all not-yet-zeroed inode tables as
246 zeroed. This significantly speeds up filesystem initialization. This is set
250 Do not attempt to discard blocks at mkfs time.
253 .BI \-f " fragment-size"
254 Specify the size of fragments in bytes.
259 to create a filesystem, even if the specified device is not a partition
260 on a block special device, or if other parameters do not make sense.
263 to create a filesystem even if the filesystem appears to be in use
264 or is mounted (a truly dangerous thing to do), this option must be
267 .BI \-g " blocks-per-group"
268 Specify the number of blocks in a block group. There is generally no
269 reason for the user to ever set this parameter, as the default is optimal
270 for the filesystem. (For administrators who are creating
271 filesystems on RAID arrays, it is preferable to use the
273 RAID parameter as part of the
275 option rather than manipulating the number of blocks per group.)
276 This option is generally used by developers who
277 are developing test cases.
279 .BI \-G " number-of-groups"
280 Specify the number of block groups that will be packed together to
281 create a larger virtual block group (or "flex_bg group") in an
282 ext4 filesystem. This improves meta-data locality and performance
283 on meta-data heavy workloads. The number of groups must be a power
284 of 2 and may only be specified if the
286 filesystem feature is enabled.
288 .BI \-i " bytes-per-inode"
289 Specify the bytes/inode ratio.
291 creates an inode for every
293 bytes of space on the disk. The larger the
295 ratio, the fewer inodes will be created. This value generally shouldn't
296 be smaller than the blocksize of the filesystem, since in that case more
297 inodes would be made than can ever be used. Be warned that it is not
298 possible to expand the number
299 of inodes on a filesystem after it is created, so be careful deciding the
300 correct value for this parameter.
302 .BI \-I " inode-size"
303 Specify the size of each inode in bytes.
305 creates 256-byte inodes by default. In kernels after 2.6.10 and some
306 earlier vendor kernels it is possible to utilize inodes larger than
308 extended attributes for improved performance. The
310 value must be a power of 2 larger or equal to 128. The larger the
312 the more space the inode table will consume, and this reduces the usable
313 space in the filesystem and can also negatively impact performance.
315 stored in large inodes are not visible with older kernels, and such
316 filesystems will not be mountable with 2.4 kernels at all. It is not
317 possible to change this value after the filesystem is created.
320 Create the filesystem with an ext3 journal. If the
322 option is not specified, the default journal parameters will be used to
323 create an appropriately sized journal (given the size of the filesystem)
324 stored within the filesystem. Note that you must be using a kernel
325 which has ext3 support in order to actually make use of the journal.
327 .BI \-J " journal-options"
328 Create the ext3 journal using options specified on the command-line.
329 Journal options are comma
330 separated, and may take an argument using the equals ('=') sign.
331 The following journal options are supported:
334 .BI size= journal-size
335 Create an internal journal (i.e., stored inside the filesystem) of size
338 The size of the journal must be at least 1024 filesystem blocks
339 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
340 and may be no more than 102,400 filesystem blocks.
342 @JDEV@.BI device= external-journal
343 @JDEV@Attach the filesystem to the journal block device located on
344 @JDEV@.IR external-journal .
346 @JDEV@journal must already have been created using the command
348 @JDEV@.B mke2fs -O journal_dev
349 @JDEV@.I external-journal
352 @JDEV@.I external-journal
353 @JDEV@must have been created with the
354 @JDEV@same block size as the new filesystem.
355 @JDEV@In addition, while there is support for attaching
356 @JDEV@multiple filesystems to a single external journal,
357 @JDEV@the Linux kernel and
359 @JDEV@do not currently support shared external journals yet.
361 @JDEV@Instead of specifying a device name directly,
362 @JDEV@.I external-journal
363 @JDEV@can also be specified by either
364 @JDEV@.BI LABEL= label
367 @JDEV@to locate the external journal by either the volume label or UUID
368 @JDEV@stored in the ext2 superblock at the start of the journal. Use
369 @JDEV@.BR dumpe2fs (8)
370 @JDEV@to display a journal device's volume label and UUID. See also the
373 @JDEV@.BR tune2fs (8).
376 @JDEV@Only one of the
377 @JDEV@.BR size " or " device
378 @JDEV@options can be given for a filesystem.
381 Read the bad blocks list from
383 Note that the block numbers in the bad block list must be generated
384 using the same block size as used by
390 is a much simpler and less error-prone method of checking a disk for bad
391 blocks before formatting it, as
393 will automatically pass the correct parameters to the
397 .BI \-L " new-volume-label"
398 Set the volume label for the filesystem to
399 .IR new-volume-label .
400 The maximum length of the
401 volume label is 16 bytes.
403 .BI \-m " reserved-blocks-percentage"
404 Specify the percentage of the filesystem blocks reserved for
405 the super-user. This avoids fragmentation, and allows root-owned
408 to continue to function correctly after non-privileged processes are
409 prevented from writing to the filesystem. The default percentage
412 .BI \-M " last-mounted-directory"
413 Set the last mounted directory for the filesystem. This might be useful
414 for the sake of utilities that key off of the last mounted directory to
415 determine where the filesystem should be mounted.
420 to not actually create a filesystem, but display what it
421 would do if it were to create a filesystem. This can be used to
422 determine the location of the backup superblocks for a particular
423 filesystem, so long as the
425 parameters that were passed when the
426 filesystem was originally created are used again. (With the
428 option added, of course!)
430 .BI \-N " number-of-inodes"
431 Overrides the default calculation of the number of inodes that should be
432 reserved for the filesystem (which is based on the number of blocks and
435 ratio). This allows the user to specify the number
436 of desired inodes directly.
438 .BI \-o " creator-os"
439 Overrides the default value of the "creator operating system" field of the
440 filesystem. The creator field is set by default to the name of the OS the
442 executable was compiled for.
444 .B "\-O \fIfeature\fR[,...]"
445 Create a filesystem with the given features (filesystem options),
446 overriding the default filesystem options. The features that are
447 enabled by default are specified by the
449 relation, either in the
456 subsections for the usage types as specified by the
458 option, further modified by the
460 relation found in the
462 subsections for the filesystem and usage types. See the
464 manual page for more details.
465 The filesystem type-specific configuration setting found in the
467 section will override the global default found in
470 The filesystem feature set will be further edited
471 using either the feature set specified by this option,
472 or if this option is not given, by the
474 relation for the filesystem type being created, or in the
476 section of the configuration file.
478 The filesystem feature set is comprised of a list of features, separated
479 by commas, that are to be enabled. To disable a feature, simply
480 prefix the feature name with a caret ('^') character. The
481 pseudo-filesystem feature "none" will clear all filesystem features.
485 Use hashed b-trees to speed up lookups in large directories.
488 Instead of using the indirect block scheme for storing the location of
489 data blocks in an inode, use extents instead. This is a much more
490 efficient encoding which speeds up filesystem access, especially for
494 Store file type information in directory entries.
497 Allow the per-block group metadata (allocation bitmaps and inode tables)
498 to be placed anywhere on the storage media. In addition,
500 will place the per-block group metadata together starting at the first
501 block group of each "flex_bg group". The size of the flex_bg group
502 can be specified using the
507 Create an ext3 journal (as if using the
512 @JDEV@Create an external ext3 journal on the given device
513 @JDEV@instead of a regular ext2 filesystem.
515 @JDEV@.I external-journal
516 @JDEV@must be created with the same
517 @JDEV@block size as the filesystems that will be using it.
520 Filesystem can contain files that are greater than 2GB. (Modern kernels
521 set this feature automatically when a file > 2GB is created.)
524 Reserve space so the block group descriptor table may grow in the future.
525 Useful for online resizing using
529 will attempt to reserve enough space so that the
530 filesystem may grow to 1024 times its initial size. This can be changed
536 Create a filesystem with fewer superblock backup copies
537 (saves space on large filesystems).
540 Create a filesystem without initializing all of the block groups. This
541 feature also enables checksums and highest-inode-used statistics in each
542 blockgroup. This feature can
543 speed up filesystem creation time noticeably (if lazy_itable_init is
544 enabled), and can also reduce
546 time dramatically. It is only supported by the ext4 filesystem in
547 recent Linux kernels.
551 Quiet execution. Useful if
556 Set the filesystem revision for the new filesystem. Note that 1.2
557 kernels only support revision 0 filesystems. The default is to
558 create revision 1 filesystems.
561 Write superblock and group descriptors only. This is useful if all of
562 the superblock and backup superblocks are corrupted, and a last-ditch
563 recovery method is desired. It causes
566 superblock and group descriptors, while not touching the inode table
567 and the block and inode bitmaps. The
569 program should be run immediately after this option is used, and there
570 is no guarantee that any data will be salvageable. It is critical to
571 specify the correct filesystem blocksize when using this option,
572 or there is no chance of recovery.
575 .\" Check the device for bad blocks before creating the file system
576 .\" using the specified test.
579 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is to be created.
580 If this option is not specified,
582 will pick a default either via how
583 the command was run (for example, using a name of the form mkfs.ext2,
584 mkfs.ext3, etc.) or via a default as defined by the
585 .BR /etc/mke2fs.conf (5)
586 file. This option controls which filesystem options are used by
587 default, based on the
589 configuration stanza in
590 .BR /etc/mke2fs.conf (5).
594 option is used to explicitly add or remove filesystem options that
595 should be set in the newly created filesystem, the
596 resulting filesystem may not be supported by the requested
598 (e.g., "\fBmke2fs \-t ext3 \-O extents /dev/sdXX\fR" will create a
599 filesystem that is not supported by the ext3 implementation as found in
600 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
601 will create a filesystem that does not have a journal and hence will not
602 be supported by the ext3 filesystem code in the Linux kernel.)
604 .BI \-T " usage-type[,...]"
605 Specify how the filesystem is going to be used, so that
607 can choose optimal filesystem parameters for that use. The usage
608 types that are supported are defined in the configuration file
609 .BR /etc/mke2fs.conf (5).
610 The user may specify one or more usage types
611 using a comma separated list.
613 If this option is is not specified,
615 will pick a single default usage type based on the size of the filesystem to
616 be created. If the filesystem size is less than or equal to 3 megabytes,
618 will use the filesystem type
620 If the filesystem size is greater than 3 but less than or equal to
623 will use the filesystem type
625 If the filesystem size is greater than or equal to 4 terabytes but less than
628 will use the filesystem type
630 If the filesystem size is greater than or equal to 16 terabytes,
632 will use the filesystem type
636 will use the default filesystem type
640 Create the filesystem with the specified UUID.
646 Print the version number of
652 If set to non-zero integer value, its value is used to determine how often
654 is called during inode table initialization.
657 Determines the location of the configuration file (see
658 .BR mke2fs.conf (5)).
660 .BI MKE2FS_FIRST_META_BG
661 If set to non-zero integer value, its value is used to determine first meta
662 block group. This is mostly for debugging purposes.
664 .BI MKE2FS_DEVICE_SECTSIZE
665 If set to non-zero integer value, its value is used to determine physical
669 .BI MKE2FS_SKIP_CHECK_MSG
670 If set, do not show the message of filesystem automatic check caused by
671 mount count or check interval.
675 has been written by Theodore Ts'o <tytso@mit.edu>.
680 option but currently ignores it because the second
681 extended file system does not support fragments yet.
683 There may be other ones. Please, report them to the author.
686 is part of the e2fsprogs package and is available from
687 http://e2fsprogs.sourceforge.net.