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
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 .BI \-f " fragment-size"
243 Specify the size of fragments in bytes.
248 to create a filesystem, even if the specified device is not a partition
249 on a block special device, or if other parameters do not make sense.
252 to create a filesystem even if the filesystem appears to be in use
253 or is mounted (a truly dangerous thing to do), this option must be
256 .BI \-g " blocks-per-group"
257 Specify the number of blocks in a block group. There is generally no
258 reason for the user to ever set this parameter, as the default is optimal
259 for the filesystem. (For administrators who are creating
260 filesystems on RAID arrays, it is preferable to use the
262 RAID parameter as part of the
264 option rather than manipulating the number of blocks per group.)
265 This option is generally used by developers who
266 are developing test cases.
268 .BI \-G " number-of-groups"
269 Specify the number of block groups that will be packed together to
270 create one large virtual block group on an ext4 filesystem. This
271 improves meta-data locality and performance on meta-data heavy
272 workloads. The number of groups must be a power of 2 and may only be
273 specified if the flex_bg filesystem feature is enabled.
275 .BI \-i " bytes-per-inode"
276 Specify the bytes/inode ratio.
278 creates an inode for every
280 bytes of space on the disk. The larger the
282 ratio, the fewer inodes will be created. This value generally shouldn't
283 be smaller than the blocksize of the filesystem, since in that case more
284 inodes would be made than can ever be used. Be warned that it is not
285 possible to expand the number
286 of inodes on a filesystem after it is created, so be careful deciding the
287 correct value for this parameter.
289 .BI \-I " inode-size"
290 Specify the size of each inode in bytes.
292 creates 256-byte inodes by default. In kernels after 2.6.10 and some
293 earlier vendor kernels it is possible to utilize inodes larger than
295 extended attributes for improved performance. The
297 value must be a power of 2 larger or equal to 128. The larger the
299 the more space the inode table will consume, and this reduces the usable
300 space in the filesystem and can also negatively impact performance.
302 stored in large inodes are not visible with older kernels, and such
303 filesystems will not be mountable with 2.4 kernels at all. It is not
304 possible to change this value after the filesystem is created.
307 Create the filesystem with an ext3 journal. If the
309 option is not specified, the default journal parameters will be used to
310 create an appropriately sized journal (given the size of the filesystem)
311 stored within the filesystem. Note that you must be using a kernel
312 which has ext3 support in order to actually make use of the journal.
314 .BI \-J " journal-options"
315 Create the ext3 journal using options specified on the command-line.
316 Journal options are comma
317 separated, and may take an argument using the equals ('=') sign.
318 The following journal options are supported:
321 .BI size= journal-size
322 Create an internal journal (i.e., stored inside the filesystem) of size
325 The size of the journal must be at least 1024 filesystem blocks
326 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
327 and may be no more than 102,400 filesystem blocks.
329 @JDEV@.BI device= external-journal
330 @JDEV@Attach the filesystem to the journal block device located on
331 @JDEV@.IR external-journal .
333 @JDEV@journal must already have been created using the command
335 @JDEV@.B mke2fs -O journal_dev
336 @JDEV@.I external-journal
339 @JDEV@.I external-journal
340 @JDEV@must have been created with the
341 @JDEV@same block size as the new filesystem.
342 @JDEV@In addition, while there is support for attaching
343 @JDEV@multiple filesystems to a single external journal,
344 @JDEV@the Linux kernel and
346 @JDEV@do not currently support shared external journals yet.
348 @JDEV@Instead of specifying a device name directly,
349 @JDEV@.I external-journal
350 @JDEV@can also be specified by either
351 @JDEV@.BI LABEL= label
354 @JDEV@to locate the external journal by either the volume label or UUID
355 @JDEV@stored in the ext2 superblock at the start of the journal. Use
356 @JDEV@.BR dumpe2fs (8)
357 @JDEV@to display a journal device's volume label and UUID. See also the
360 @JDEV@.BR tune2fs (8).
363 @JDEV@Only one of the
364 @JDEV@.BR size " or " device
365 @JDEV@options can be given for a filesystem.
368 Read the bad blocks list from
370 Note that the block numbers in the bad block list must be generated
371 using the same block size as used by
377 is a much simpler and less error-prone method of checking a disk for bad
378 blocks before formatting it, as
380 will automatically pass the correct parameters to the
384 .BI \-L " new-volume-label"
385 Set the volume label for the filesystem to
386 .IR new-volume-label .
387 The maximum length of the
388 volume label is 16 bytes.
390 .BI \-m " reserved-blocks-percentage"
391 Specify the percentage of the filesystem blocks reserved for
392 the super-user. This avoids fragmentation, and allows root-owned
395 to continue to function correctly after non-privileged processes are
396 prevented from writing to the filesystem. The default percentage
399 .BI \-M " last-mounted-directory"
400 Set the last mounted directory for the filesystem. This might be useful
401 for the sake of utilities that key off of the last mounted directory to
402 determine where the filesystem should be mounted.
407 to not actually create a filesystem, but display what it
408 would do if it were to create a filesystem. This can be used to
409 determine the location of the backup superblocks for a particular
410 filesystem, so long as the
412 parameters that were passed when the
413 filesystem was originally created are used again. (With the
415 option added, of course!)
417 .BI \-N " number-of-inodes"
418 Overrides the default calculation of the number of inodes that should be
419 reserved for the filesystem (which is based on the number of blocks and
422 ratio). This allows the user to specify the number
423 of desired inodes directly.
425 .BI \-o " creator-os"
426 Overrides the default value of the "creator operating system" field of the
427 filesystem. The creator field is set by default to the name of the OS the
429 executable was compiled for.
431 .B "\-O \fIfeature\fR[,...]"
432 Create a filesystem with the given features (filesystem options),
433 overriding the default filesystem options. The features that are
434 enabled by default are specified by the
436 relation, either in the
443 subsections for the usage types as specified by the
445 option, further modified by the
447 relation found in the
449 subsections for the filesystem and usage types. See the
451 manual page for more details.
452 The filesystem type-specific configuration setting found in the
454 section will override the global default found in
457 The filesystem feature set will be further edited
458 using either the feature set specified by this option,
459 or if this option is not given, by the
461 relation for the filesystem type being created, or in the
463 section of the configuration file.
465 The filesystem feature set is comprised of a list of features, separated
466 by commas, that are to be enabled. To disable a feature, simply
467 prefix the feature name with a caret ('^') character. The
468 pseudo-filesystem feature "none" will clear all filesystem features.
472 Filesystem can contain files that are greater than 2GB. (Modern kernels
473 set this feature automatically when a file > 2GB is created.)
476 Use hashed b-trees to speed up lookups in large directories.
479 Store file type information in directory entries.
482 Allow bitmaps and inode tables for a block group to be placed anywhere
483 on the storage media (use with \-G option to group meta-data in order
484 to create a large virtual block group).
487 Create an ext3 journal (as if using the
492 @JDEV@Create an external ext3 journal on the given device
493 @JDEV@instead of a regular ext2 filesystem.
495 @JDEV@.I external-journal
496 @JDEV@must be created with the same
497 @JDEV@block size as the filesystems that will be using it.
500 Instead of using the indirect block scheme for storing the location of
501 data blocks in an inode, use extents instead. This is a much more
502 efficient encoding which speeds up filesystem access, especially for
506 Create a filesystem without initializing all of the block groups. This
507 feature also enables checksums and highest-inode-used statistics in each
508 blockgroup. This feature can
509 speed up filesystem creation time noticeably (if lazy_itable_init is
510 enabled), and can also reduce
512 time dramatically. It is only supported by the ext4 filesystem in
513 recent Linux kernels.
516 Reserve space so the block group descriptor table may grow in the future.
517 Useful for online resizing using
521 will attempt to reserve enough space so that the
522 filesystem may grow to 1024 times its initial size. This can be changed
528 Create a filesystem with fewer superblock backup copies
529 (saves space on large filesystems).
533 Quiet execution. Useful if
538 Set the filesystem revision for the new filesystem. Note that 1.2
539 kernels only support revision 0 filesystems. The default is to
540 create revision 1 filesystems.
543 Write superblock and group descriptors only. This is useful if all of
544 the superblock and backup superblocks are corrupted, and a last-ditch
545 recovery method is desired. It causes
548 superblock and group descriptors, while not touching the inode table
549 and the block and inode bitmaps. The
551 program should be run immediately after this option is used, and there
552 is no guarantee that any data will be salvageable. It is critical to
553 specify the correct filesystem blocksize when using this option,
554 or there is no chance of recovery.
557 .\" Check the device for bad blocks before creating the file system
558 .\" using the specified test.
561 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is to be created.
562 If this option is not specified,
564 will pick a default either via how
565 the command was run (for example, using a name of the form mkfs.ext2,
566 mkfs.ext3, etc.) or via a default as defined by the
567 .BR /etc/mke2fs.conf (5)
568 file. This option controls which filesystem options are used by
569 default, based on the
571 configuration stanza in
572 .BR /etc/mke2fs.conf (5).
576 option is used to explicitly add or remove filesystem options that
577 should be set in the newly created filesystem, the
578 resulting filesystem may not be supported by the requested
580 (e.g., "\fBmke2fs \-t ext3 \-O extents /dev/sdXX\fR" will create a
581 filesystem that is not supported by the ext3 implementation as found in
582 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
583 will create a filesystem that does not have a journal and hence will not
584 be supported by the ext3 filesystem code in the Linux kernel.)
586 .BI \-T " usage-type[,...]"
587 Specify how the filesystem is going to be used, so that
589 can choose optimal filesystem parameters for that use. The usage
590 types that are supported are defined in the configuration file
591 .BR /etc/mke2fs.conf (5).
592 The user may specify one or more usage types
593 using a comma separated list.
595 If this option is is not specified,
597 will pick a single default usage type based on the size of the filesystem to
598 be created. If the filesystem size is less than or equal to 3 megabytes,
600 will use the filesystem type
602 If the filesystem size is greater than 3 but less than or equal to
605 will use the filesystem
609 will use the default filesystem type
613 Create the filesystem with the specified UUID.
619 Print the version number of
625 has been written by Theodore Ts'o <tytso@mit.edu>.
630 option but currently ignores it because the second
631 extended file system does not support fragments yet.
633 There may be other ones. Please, report them to the author.
636 is part of the e2fsprogs package and is available from
637 http://e2fsprogs.sourceforge.net.