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
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 .BI \-E " extended-options"
191 Set extended options for the filesystem. Extended options are comma
192 separated, and may take an argument using the equals ('=') sign. The
196 in earlier versions of
200 option is still accepted for backwards compatibility. The
201 following extended options are supported:
204 .BI stride= stride-size
205 Configure the filesystem for a RAID array with
207 filesystem blocks. This is the number of blocks read or written to disk
208 before moving to the next disk, which is sometimes referred to as the
210 This mostly affects placement of filesystem metadata like bitmaps at
212 time to avoid placing them on a single disk, which can hurt performance.
213 It may also be used by the block allocator.
215 .BI stripe-width= stripe-width
216 Configure the filesystem for a RAID array with
218 filesystem blocks per stripe. This is typically stride-size * N, where
219 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
220 parity disk, so N will be the number of disks in the array minus 1).
221 This allows the block allocator to prevent read-modify-write of the
222 parity in a RAID stripe if possible when the data is written.
224 .BI resize= max-online-resize
225 Reserve enough space so that the block group descriptor table can grow
226 to support a filesystem that has
230 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
231 If enabled and the uninit_bg feature is enabled, the inode table will
232 not be fully initialized by
234 This speeds up filesystem
235 initialization noticeably, but it requires the kernel to finish
236 initializing the filesystem in the background when the filesystem is
237 first mounted. If the option value is omitted, it defaults to 1 to
238 enable lazy inode table initialization.
241 Set a flag in the filesystem superblock indicating that it may be
242 mounted using experimental kernel code, such as the ext4dev filesystem.
245 .BI \-f " fragment-size"
246 Specify the size of fragments in bytes.
251 to create a filesystem, even if the specified device is not a partition
252 on a block special device, or if other parameters do not make sense.
255 to create a filesystem even if the filesystem appears to be in use
256 or is mounted (a truly dangerous thing to do), this option must be
259 .BI \-g " blocks-per-group"
260 Specify the number of blocks in a block group. There is generally no
261 reason for the user to ever set this parameter, as the default is optimal
262 for the filesystem. (For administrators who are creating
263 filesystems on RAID arrays, it is preferable to use the
265 RAID parameter as part of the
267 option rather than manipulating the number of blocks per group.)
268 This option is generally used by developers who
269 are developing test cases.
271 .BI \-G " number-of-groups"
272 Specify the number of block groups that will be packed together to
273 create a larger virtual block group (or "flex_bg group") in an
274 ext4 filesystem. This improves meta-data locality and performance
275 on meta-data heavy workloads. The number of groups must be a power
276 of 2 and may only be specified if the
278 filesystem feature is enabled.
280 .BI \-i " bytes-per-inode"
281 Specify the bytes/inode ratio.
283 creates an inode for every
285 bytes of space on the disk. The larger the
287 ratio, the fewer inodes will be created. This value generally shouldn't
288 be smaller than the blocksize of the filesystem, since in that case more
289 inodes would be made than can ever be used. Be warned that it is not
290 possible to expand the number
291 of inodes on a filesystem after it is created, so be careful deciding the
292 correct value for this parameter.
294 .BI \-I " inode-size"
295 Specify the size of each inode in bytes.
297 creates 256-byte inodes by default. In kernels after 2.6.10 and some
298 earlier vendor kernels it is possible to utilize inodes larger than
300 extended attributes for improved performance. The
302 value must be a power of 2 larger or equal to 128. The larger the
304 the more space the inode table will consume, and this reduces the usable
305 space in the filesystem and can also negatively impact performance.
307 stored in large inodes are not visible with older kernels, and such
308 filesystems will not be mountable with 2.4 kernels at all. It is not
309 possible to change this value after the filesystem is created.
312 Create the filesystem with an ext3 journal. If the
314 option is not specified, the default journal parameters will be used to
315 create an appropriately sized journal (given the size of the filesystem)
316 stored within the filesystem. Note that you must be using a kernel
317 which has ext3 support in order to actually make use of the journal.
319 .BI \-J " journal-options"
320 Create the ext3 journal using options specified on the command-line.
321 Journal options are comma
322 separated, and may take an argument using the equals ('=') sign.
323 The following journal options are supported:
326 .BI size= journal-size
327 Create an internal journal (i.e., stored inside the filesystem) of size
330 The size of the journal must be at least 1024 filesystem blocks
331 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
332 and may be no more than 102,400 filesystem blocks.
334 @JDEV@.BI device= external-journal
335 @JDEV@Attach the filesystem to the journal block device located on
336 @JDEV@.IR external-journal .
338 @JDEV@journal must already have been created using the command
340 @JDEV@.B mke2fs -O journal_dev
341 @JDEV@.I external-journal
344 @JDEV@.I external-journal
345 @JDEV@must have been created with the
346 @JDEV@same block size as the new filesystem.
347 @JDEV@In addition, while there is support for attaching
348 @JDEV@multiple filesystems to a single external journal,
349 @JDEV@the Linux kernel and
351 @JDEV@do not currently support shared external journals yet.
353 @JDEV@Instead of specifying a device name directly,
354 @JDEV@.I external-journal
355 @JDEV@can also be specified by either
356 @JDEV@.BI LABEL= label
359 @JDEV@to locate the external journal by either the volume label or UUID
360 @JDEV@stored in the ext2 superblock at the start of the journal. Use
361 @JDEV@.BR dumpe2fs (8)
362 @JDEV@to display a journal device's volume label and UUID. See also the
365 @JDEV@.BR tune2fs (8).
368 @JDEV@Only one of the
369 @JDEV@.BR size " or " device
370 @JDEV@options can be given for a filesystem.
373 Keep, do not attempt to discard blocks at mkfs time (discarding blocks initially
374 is useful on solid state devices and sparse / thin-provisioned storage).
377 Read the bad blocks list from
379 Note that the block numbers in the bad block list must be generated
380 using the same block size as used by
386 is a much simpler and less error-prone method of checking a disk for bad
387 blocks before formatting it, as
389 will automatically pass the correct parameters to the
393 .BI \-L " new-volume-label"
394 Set the volume label for the filesystem to
395 .IR new-volume-label .
396 The maximum length of the
397 volume label is 16 bytes.
399 .BI \-m " reserved-blocks-percentage"
400 Specify the percentage of the filesystem blocks reserved for
401 the super-user. This avoids fragmentation, and allows root-owned
404 to continue to function correctly after non-privileged processes are
405 prevented from writing to the filesystem. The default percentage
408 .BI \-M " last-mounted-directory"
409 Set the last mounted directory for the filesystem. This might be useful
410 for the sake of utilities that key off of the last mounted directory to
411 determine where the filesystem should be mounted.
416 to not actually create a filesystem, but display what it
417 would do if it were to create a filesystem. This can be used to
418 determine the location of the backup superblocks for a particular
419 filesystem, so long as the
421 parameters that were passed when the
422 filesystem was originally created are used again. (With the
424 option added, of course!)
426 .BI \-N " number-of-inodes"
427 Overrides the default calculation of the number of inodes that should be
428 reserved for the filesystem (which is based on the number of blocks and
431 ratio). This allows the user to specify the number
432 of desired inodes directly.
434 .BI \-o " creator-os"
435 Overrides the default value of the "creator operating system" field of the
436 filesystem. The creator field is set by default to the name of the OS the
438 executable was compiled for.
440 .B "\-O \fIfeature\fR[,...]"
441 Create a filesystem with the given features (filesystem options),
442 overriding the default filesystem options. The features that are
443 enabled by default are specified by the
445 relation, either in the
452 subsections for the usage types as specified by the
454 option, further modified by the
456 relation found in the
458 subsections for the filesystem and usage types. See the
460 manual page for more details.
461 The filesystem type-specific configuration setting found in the
463 section will override the global default found in
466 The filesystem feature set will be further edited
467 using either the feature set specified by this option,
468 or if this option is not given, by the
470 relation for the filesystem type being created, or in the
472 section of the configuration file.
474 The filesystem feature set is comprised of a list of features, separated
475 by commas, that are to be enabled. To disable a feature, simply
476 prefix the feature name with a caret ('^') character. The
477 pseudo-filesystem feature "none" will clear all filesystem features.
481 Use hashed b-trees to speed up lookups in large directories.
484 Instead of using the indirect block scheme for storing the location of
485 data blocks in an inode, use extents instead. This is a much more
486 efficient encoding which speeds up filesystem access, especially for
490 Store file type information in directory entries.
493 Allow the per-block group metadata (allocation bitmaps and inode tables)
494 to be placed anywhere on the storage media. In addition,
496 will place the per-block group metadata together starting at the first
497 block group of each "flex_bg group". The size of the flex_bg group
498 can be specified using the
503 Create an ext3 journal (as if using the
508 @JDEV@Create an external ext3 journal on the given device
509 @JDEV@instead of a regular ext2 filesystem.
511 @JDEV@.I external-journal
512 @JDEV@must be created with the same
513 @JDEV@block size as the filesystems that will be using it.
516 Filesystem can contain files that are greater than 2GB. (Modern kernels
517 set this feature automatically when a file > 2GB is created.)
520 Reserve space so the block group descriptor table may grow in the future.
521 Useful for online resizing using
525 will attempt to reserve enough space so that the
526 filesystem may grow to 1024 times its initial size. This can be changed
532 Create a filesystem with fewer superblock backup copies
533 (saves space on large filesystems).
536 Create a filesystem without initializing all of the block groups. This
537 feature also enables checksums and highest-inode-used statistics in each
538 blockgroup. This feature can
539 speed up filesystem creation time noticeably (if lazy_itable_init is
540 enabled), and can also reduce
542 time dramatically. It is only supported by the ext4 filesystem in
543 recent Linux kernels.
547 Quiet execution. Useful if
552 Set the filesystem revision for the new filesystem. Note that 1.2
553 kernels only support revision 0 filesystems. The default is to
554 create revision 1 filesystems.
557 Write superblock and group descriptors only. This is useful if all of
558 the superblock and backup superblocks are corrupted, and a last-ditch
559 recovery method is desired. It causes
562 superblock and group descriptors, while not touching the inode table
563 and the block and inode bitmaps. The
565 program should be run immediately after this option is used, and there
566 is no guarantee that any data will be salvageable. It is critical to
567 specify the correct filesystem blocksize when using this option,
568 or there is no chance of recovery.
571 .\" Check the device for bad blocks before creating the file system
572 .\" using the specified test.
575 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is to be created.
576 If this option is not specified,
578 will pick a default either via how
579 the command was run (for example, using a name of the form mkfs.ext2,
580 mkfs.ext3, etc.) or via a default as defined by the
581 .BR /etc/mke2fs.conf (5)
582 file. This option controls which filesystem options are used by
583 default, based on the
585 configuration stanza in
586 .BR /etc/mke2fs.conf (5).
590 option is used to explicitly add or remove filesystem options that
591 should be set in the newly created filesystem, the
592 resulting filesystem may not be supported by the requested
594 (e.g., "\fBmke2fs \-t ext3 \-O extents /dev/sdXX\fR" will create a
595 filesystem that is not supported by the ext3 implementation as found in
596 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
597 will create a filesystem that does not have a journal and hence will not
598 be supported by the ext3 filesystem code in the Linux kernel.)
600 .BI \-T " usage-type[,...]"
601 Specify how the filesystem is going to be used, so that
603 can choose optimal filesystem parameters for that use. The usage
604 types that are supported are defined in the configuration file
605 .BR /etc/mke2fs.conf (5).
606 The user may specify one or more usage types
607 using a comma separated list.
609 If this option is is not specified,
611 will pick a single default usage type based on the size of the filesystem to
612 be created. If the filesystem size is less than or equal to 3 megabytes,
614 will use the filesystem type
616 If the filesystem size is greater than 3 but less than or equal to
619 will use the filesystem
623 will use the default filesystem type
627 Create the filesystem with the specified UUID.
633 Print the version number of
639 has been written by Theodore Ts'o <tytso@mit.edu>.
644 option but currently ignores it because the second
645 extended file system does not support fragments yet.
647 There may be other ones. Please, report them to the author.
650 is part of the e2fsprogs package and is available from
651 http://e2fsprogs.sourceforge.net.