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 root_owner [=uid:gid]
278 Specify the numeric user and group ID of the root directory. If no UID:GID
279 is specified, use the user and group ID of the user running \fBmke2fs\fR.
280 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
281 set by default to the UID and GID of the user running the mke2fs command.
282 The \fBroot_owner=\fR option allows explicitly specifying these values,
283 and avoid side-effects for users that do not expect the contents of the
284 filesystem to change based on the user running \fBmke2fs\fR.
287 Set a flag in the filesystem superblock indicating that it may be
288 mounted using experimental kernel code, such as the ext4dev filesystem.
291 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
292 on solid state devices and sparse / thin-provisioned storage). When the device
293 advertises that discard also zeroes data (any subsequent read after the discard
294 and before write returns zero), then mark all not-yet-zeroed inode tables as
295 zeroed. This significantly speeds up filesystem initialization. This is set
299 Do not attempt to discard blocks at mkfs time.
300 @QUOTA_MAN_COMMENT@.TP
301 @QUOTA_MAN_COMMENT@.BI quotatype
302 @QUOTA_MAN_COMMENT@Specify which quota type ('usr' or 'grp') is to be
303 @QUOTA_MAN_COMMENT@initialized. This option has effect only if the
304 @QUOTA_MAN_COMMENT@.B quota
305 @QUOTA_MAN_COMMENT@feature is set. Without this extended option, the default
306 @QUOTA_MAN_COMMENT@behavior is to initialize both user and group quotas.
309 .BI \-f " fragment-size"
310 Specify the size of fragments in bytes.
315 to create a filesystem, even if the specified device is not a partition
316 on a block special device, or if other parameters do not make sense.
319 to create a filesystem even if the filesystem appears to be in use
320 or is mounted (a truly dangerous thing to do), this option must be
323 .BI \-g " blocks-per-group"
324 Specify the number of blocks in a block group. There is generally no
325 reason for the user to ever set this parameter, as the default is optimal
326 for the filesystem. (For administrators who are creating
327 filesystems on RAID arrays, it is preferable to use the
329 RAID parameter as part of the
331 option rather than manipulating the number of blocks per group.)
332 This option is generally used by developers who
333 are developing test cases.
335 If the bigalloc feature is enabled, the
337 option will specify the number of clusters in a block group.
339 .BI \-G " number-of-groups"
340 Specify the number of block groups that will be packed together to
341 create a larger virtual block group (or "flex_bg group") in an
342 ext4 filesystem. This improves meta-data locality and performance
343 on meta-data heavy workloads. The number of groups must be a power
344 of 2 and may only be specified if the
346 filesystem feature is enabled.
348 .BI \-i " bytes-per-inode"
349 Specify the bytes/inode ratio.
351 creates an inode for every
353 bytes of space on the disk. The larger the
355 ratio, the fewer inodes will be created. This value generally shouldn't
356 be smaller than the blocksize of the filesystem, since in that case more
357 inodes would be made than can ever be used. Be warned that it is not
358 possible to change this ratio on a filesystem after it is created, so be
359 careful deciding the correct value for this parameter. Note that resizing
360 a filesystem changes the numer of inodes to maintain this ratio.
362 .BI \-I " inode-size"
363 Specify the size of each inode in bytes.
366 value must be a power of 2 larger or equal to 128. The larger the
368 the more space the inode table will consume, and this reduces the usable
369 space in the filesystem and can also negatively impact performance.
371 possible to change this value after the filesystem is created.
373 In kernels after 2.6.10 and some
374 earlier vendor kernels it is possible to utilize inodes larger than
376 extended attributes for improved performance.
378 stored in large inodes are not visible with older kernels, and such
379 filesystems will not be mountable with 2.4 kernels at all.
381 The default inode size is controlled by the
385 file shipped with e2fsprogs, the default inode size is 256 bytes for
386 most file systems, except for small file systems where the inode size
390 Create the filesystem with an ext3 journal. If the
392 option is not specified, the default journal parameters will be used to
393 create an appropriately sized journal (given the size of the filesystem)
394 stored within the filesystem. Note that you must be using a kernel
395 which has ext3 support in order to actually make use of the journal.
397 .BI \-J " journal-options"
398 Create the ext3 journal using options specified on the command-line.
399 Journal options are comma
400 separated, and may take an argument using the equals ('=') sign.
401 The following journal options are supported:
404 .BI size= journal-size
405 Create an internal journal (i.e., stored inside the filesystem) of size
408 The size of the journal must be at least 1024 filesystem blocks
409 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
410 and may be no more than 10,240,000 filesystem blocks or half the total
411 file system size (whichever is smaller)
413 .BI location =journal-location
414 Specify the location of the journal. The argument
416 can either be specified as a block number, or if the number has a units
417 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
418 beginning of the file system.
420 @JDEV@.BI device= external-journal
421 @JDEV@Attach the filesystem to the journal block device located on
422 @JDEV@.IR external-journal .
424 @JDEV@journal must already have been created using the command
426 @JDEV@.B mke2fs -O journal_dev
427 @JDEV@.I external-journal
430 @JDEV@.I external-journal
431 @JDEV@must have been created with the
432 @JDEV@same block size as the new filesystem.
433 @JDEV@In addition, while there is support for attaching
434 @JDEV@multiple filesystems to a single external journal,
435 @JDEV@the Linux kernel and
437 @JDEV@do not currently support shared external journals yet.
439 @JDEV@Instead of specifying a device name directly,
440 @JDEV@.I external-journal
441 @JDEV@can also be specified by either
442 @JDEV@.BI LABEL= label
445 @JDEV@to locate the external journal by either the volume label or UUID
446 @JDEV@stored in the ext2 superblock at the start of the journal. Use
447 @JDEV@.BR dumpe2fs (8)
448 @JDEV@to display a journal device's volume label and UUID. See also the
451 @JDEV@.BR tune2fs (8).
454 @JDEV@Only one of the
455 @JDEV@.BR size " or " device
456 @JDEV@options can be given for a filesystem.
459 Read the bad blocks list from
461 Note that the block numbers in the bad block list must be generated
462 using the same block size as used by
468 is a much simpler and less error-prone method of checking a disk for bad
469 blocks before formatting it, as
471 will automatically pass the correct parameters to the
475 .BI \-L " new-volume-label"
476 Set the volume label for the filesystem to
477 .IR new-volume-label .
478 The maximum length of the
479 volume label is 16 bytes.
481 .BI \-m " reserved-blocks-percentage"
482 Specify the percentage of the filesystem blocks reserved for
483 the super-user. This avoids fragmentation, and allows root-owned
486 to continue to function correctly after non-privileged processes are
487 prevented from writing to the filesystem. The default percentage
490 .BI \-M " last-mounted-directory"
491 Set the last mounted directory for the filesystem. This might be useful
492 for the sake of utilities that key off of the last mounted directory to
493 determine where the filesystem should be mounted.
498 to not actually create a filesystem, but display what it
499 would do if it were to create a filesystem. This can be used to
500 determine the location of the backup superblocks for a particular
501 filesystem, so long as the
503 parameters that were passed when the
504 filesystem was originally created are used again. (With the
506 option added, of course!)
508 .BI \-N " number-of-inodes"
509 Overrides the default calculation of the number of inodes that should be
510 reserved for the filesystem (which is based on the number of blocks and
513 ratio). This allows the user to specify the number
514 of desired inodes directly.
516 .BI \-o " creator-os"
517 Overrides the default value of the "creator operating system" field of the
518 filesystem. The creator field is set by default to the name of the OS the
520 executable was compiled for.
522 .B "\-O \fR[^]\fIfeature\fR[,...]"
523 Create a filesystem with the given features (filesystem options),
524 overriding the default filesystem options. The features that are
525 enabled by default are specified by the
527 relation, either in the
534 subsections for the usage types as specified by the
536 option, further modified by the
538 relation found in the
540 subsections for the filesystem and usage types. See the
542 manual page for more details.
543 The filesystem type-specific configuration setting found in the
545 section will override the global default found in
548 The filesystem feature set will be further edited
549 using either the feature set specified by this option,
550 or if this option is not given, by the
552 relation for the filesystem type being created, or in the
554 section of the configuration file.
556 The filesystem feature set is comprised of a list of features, separated
557 by commas, that are to be enabled. To disable a feature, simply
558 prefix the feature name with a caret ('^') character.
559 Features with dependencies will not be removed successfully.
560 The pseudo-filesystem feature "none" will clear all filesystem features.
562 For more information about the features which can be set, please see
567 Quiet execution. Useful if
572 Set the filesystem revision for the new filesystem. Note that 1.2
573 kernels only support revision 0 filesystems. The default is to
574 create revision 1 filesystems.
577 Write superblock and group descriptors only. This is useful if all of
578 the superblock and backup superblocks are corrupted, and a last-ditch
579 recovery method is desired. It causes
582 superblock and group descriptors, while not touching the inode table
583 and the block and inode bitmaps. The
585 program should be run immediately after this option is used, and there
586 is no guarantee that any data will be salvageable. It is critical to
587 specify the correct filesystem blocksize when using this option,
588 or there is no chance of recovery.
591 .\" Check the device for bad blocks before creating the file system
592 .\" using the specified test.
595 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
597 If this option is not specified,
599 will pick a default either via how
600 the command was run (for example, using a name of the form mkfs.ext2,
601 mkfs.ext3, etc.) or via a default as defined by the
603 file. This option controls which filesystem options are used by
604 default, based on the
606 configuration stanza in
607 .BR /etc/mke2fs.conf .
611 option is used to explicitly add or remove filesystem options that
612 should be set in the newly created filesystem, the
613 resulting filesystem may not be supported by the requested
615 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
616 filesystem that is not supported by the ext3 implementation as found in
617 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
618 will create a filesystem that does not have a journal and hence will not
619 be supported by the ext3 filesystem code in the Linux kernel.)
621 .BI \-T " usage-type[,...]"
622 Specify how the filesystem is going to be used, so that
624 can choose optimal filesystem parameters for that use. The usage
625 types that are supported are defined in the configuration file
626 .BR /etc/mke2fs.conf .
627 The user may specify one or more usage types
628 using a comma separated list.
630 If this option is is not specified,
632 will pick a single default usage type based on the size of the filesystem to
633 be created. If the filesystem size is less than or equal to 3 megabytes,
635 will use the filesystem type
637 If the filesystem size is greater than 3 but less than or equal to
640 will use the filesystem type
642 If the filesystem size is greater than or equal to 4 terabytes but less than
645 will use the filesystem type
647 If the filesystem size is greater than or equal to 16 terabytes,
649 will use the filesystem type
653 will use the default filesystem type
657 Create the filesystem with the specified UUID.
663 Print the version number of
669 If set to non-zero integer value, its value is used to determine how often
671 is called during inode table initialization.
674 Determines the location of the configuration file (see
675 .BR mke2fs.conf (5)).
677 .BI MKE2FS_FIRST_META_BG
678 If set to non-zero integer value, its value is used to determine first meta
679 block group. This is mostly for debugging purposes.
681 .BI MKE2FS_DEVICE_SECTSIZE
682 If set to non-zero integer value, its value is used to determine physical
686 .BI MKE2FS_SKIP_CHECK_MSG
687 If set, do not show the message of filesystem automatic check caused by
688 mount count or check interval.
692 has been written by Theodore Ts'o <tytso@mit.edu>.
697 option but currently ignores it because the second
698 extended file system does not support fragments yet.
700 There may be other ones. Please, report them to the author.
703 is part of the e2fsprogs package and is available from
704 http://e2fsprogs.sourceforge.net.