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 filesystem
56 .I reserved-blocks-percentage
89 .I last-mounted-directory
110 @JDEV@.B "mke2fs \-O journal_dev"
115 .\" No external-journal specific journal options yet (size is ignored)
118 .\" @JDEV@.I journal-options
122 @JDEV@.I volume-label
133 @JDEV@.I external-journal
135 @JDEV@.I blocks-count
139 is used to create an ext2/ext3 filesystem (usually in a disk partition).
141 is the special file corresponding to the device (e.g
144 is the number of blocks on the device. If omitted,
146 automagically figures the file system size. If called as
148 a journal is created as if the
150 option was specified.
153 .BI \-b " block-size"
154 Specify the size of blocks in bytes. Valid block-size values are 1024,
155 2048 and 4096 bytes per block. If omitted,
156 block-size is heuristically determined by the filesystem size and
157 the expected usage of the filesystem (see the
163 will use heuristics to determine the
164 appropriate block size, with the constraint that the block size will be
167 bytes. This is useful for certain hardware devices which require that
168 the blocksize be a multiple of 2k.
171 Check the device for bad blocks before creating the file system. If
172 this option is specified twice, then a slower read-write
173 test is used instead of a fast read-only test.
175 .BI \-E " extended-options"
176 Set extended options for the filesystem. Extended options are comma
177 separated, and may take an argument using the equals ('=') sign. The
181 in earlier versions of
185 option is still accepted for backwards compatibility. The
186 following extended options are supported:
189 .BI stride= stride-size
190 Configure the filesystem for a RAID array with
192 filesystem blocks. This is the number of blocks read or written to disk
193 before moving to the next disk, which is sometimes referred to as the
195 This mostly affects placement of filesystem metadata like bitmaps at
197 time to avoid placing them on a single disk, which can hurt performance.
198 It may also be used by the block allocator.
200 .BI stripe-width= stripe-width
201 Configure the filesystem for a RAID array with
203 filesystem blocks per stripe. This is typically stride-size * N, where
204 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
205 parity disk, so N will be the number of disks in the array minus 1).
206 This allows the block allocator to prevent read-modify-write of the
207 parity in a RAID stripe if possible when the data is written.
209 .BI resize= max-online-resize
210 Reserve enough space so that the block group descriptor table can grow
211 to support a filesystem that has
215 .B lazy_itable_init\fR[\fb= \fI<0 to disable, 1 to enable>\fR]
216 If enabled and the uninit_bg feature is enabled, the inode table will
217 not be fully initialized by
219 This speeds up filesystem
220 initialization noticeably, but it requires the kernel to finish
221 initializing the filesystem in the background when the filesystem is
222 first mounted. If the option value is omitted, it defaults to 1 to
223 enable lazy inode table initialization.
226 Set a flag in the filesystem superblock indicating that it may be
227 mounted using experimental kernel code, such as the ext4dev filesystem.
230 .BI \-f " fragment-size"
231 Specify the size of fragments in bytes.
236 to create a filesystem, even if the specified device is not a partition
237 on a block special device, or if other parameters do not make sense.
240 to create a filesystem even if the filesystem appears to be in use
241 or is mounted (a truly dangerous thing to do), this option must be
244 .BI \-g " blocks-per-group"
245 Specify the number of blocks in a block group. There is generally no
246 reason for the user to ever set this parameter, as the default is optimal
247 for the filesystem. (For administrators who are creating
248 filesystems on RAID arrays, it is preferable to use the
250 RAID parameter as part of the
252 option rather than manipulating the number of blocks per group.)
253 This option is generally used by developers who
254 are developing test cases.
256 .BI \-G " number-of-groups"
257 Specify the number of block groups that will be packed together to
258 create one large virtual block group on an ext4 filesystem. This
259 improves meta-data locality and performance on meta-data heavy
260 workloads. The number of groups must be a power of 2 and may only be
261 specified if the flex_bg filesystem feature is enabled.
263 .BI \-i " bytes-per-inode"
264 Specify the bytes/inode ratio.
266 creates an inode for every
268 bytes of space on the disk. The larger the
270 ratio, the fewer inodes will be created. This value generally shouldn't
271 be smaller than the blocksize of the filesystem, since in that case more
272 inodes would be made than can ever be used. Be warned that it is not
273 possible to expand the number
274 of inodes on a filesystem after it is created, so be careful deciding the
275 correct value for this parameter.
277 .BI \-I " inode-size"
278 Specify the size of each inode in bytes.
280 creates 256-byte inodes by default. In kernels after 2.6.10 and some
281 earlier vendor kernels it is possible to utilize inodes larger than
283 extended attributes for improved performance. The
285 value must be a power of 2 larger or equal to 128. The larger the
287 the more space the inode table will consume, and this reduces the usable
288 space in the filesystem and can also negatively impact performance.
290 stored in large inodes are not visible with older kernels, and such
291 filesystems will not be mountable with 2.4 kernels at all. It is not
292 possible to change this value after the filesystem is created.
295 Create the filesystem with an ext3 journal. If the
297 option is not specified, the default journal parameters will be used to
298 create an appropriately sized journal (given the size of the filesystem)
299 stored within the filesystem. Note that you must be using a kernel
300 which has ext3 support in order to actually make use of the journal.
302 .BI \-J " journal-options"
303 Create the ext3 journal using options specified on the command-line.
304 Journal options are comma
305 separated, and may take an argument using the equals ('=') sign.
306 The following journal options are supported:
309 .BI size= journal-size
310 Create an internal journal (i.e., stored inside the filesystem) of size
313 The size of the journal must be at least 1024 filesystem blocks
314 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
315 and may be no more than 102,400 filesystem blocks.
317 @JDEV@.BI device= external-journal
318 @JDEV@Attach the filesystem to the journal block device located on
319 @JDEV@.IR external-journal .
321 @JDEV@journal must already have been created using the command
323 @JDEV@.B mke2fs -O journal_dev
324 @JDEV@.I external-journal
327 @JDEV@.I external-journal
328 @JDEV@must have been created with the
329 @JDEV@same block size as the new filesystem.
330 @JDEV@In addition, while there is support for attaching
331 @JDEV@multiple filesystems to a single external journal,
332 @JDEV@the Linux kernel and
334 @JDEV@do not currently support shared external journals yet.
336 @JDEV@Instead of specifying a device name directly,
337 @JDEV@.I external-journal
338 @JDEV@can also be specified by either
339 @JDEV@.BI LABEL= label
342 @JDEV@to locate the external journal by either the volume label or UUID
343 @JDEV@stored in the ext2 superblock at the start of the journal. Use
344 @JDEV@.BR dumpe2fs (8)
345 @JDEV@to display a journal device's volume label and UUID. See also the
348 @JDEV@.BR tune2fs (8).
351 @JDEV@Only one of the
352 @JDEV@.BR size " or " device
353 @JDEV@options can be given for a filesystem.
356 Read the bad blocks list from
358 Note that the block numbers in the bad block list must be generated
359 using the same block size as used by
365 is a much simpler and less error-prone method of checking a disk for bad
366 blocks before formatting it, as
368 will automatically pass the correct parameters to the
372 .BI \-L " new-volume-label"
373 Set the volume label for the filesystem to
374 .IR new-volume-label .
375 The maximum length of the
376 volume label is 16 bytes.
378 .BI \-m " reserved-blocks-percentage"
379 Specify the percentage of the filesystem blocks reserved for
380 the super-user. This avoids fragmentation, and allows root-owned
383 to continue to function correctly after non-privileged processes are
384 prevented from writing to the filesystem. The default percentage
387 .BI \-M " last-mounted-directory"
388 Set the last mounted directory for the filesystem. This might be useful
389 for the sake of utilities that key off of the last mounted directory to
390 determine where the filesystem should be mounted.
395 to not actually create a filesystem, but display what it
396 would do if it were to create a filesystem. This can be used to
397 determine the location of the backup superblocks for a particular
398 filesystem, so long as the
400 parameters that were passed when the
401 filesystem was originally created are used again. (With the
403 option added, of course!)
405 .BI \-N " number-of-inodes"
406 Overrides the default calculation of the number of inodes that should be
407 reserved for the filesystem (which is based on the number of blocks and
410 ratio). This allows the user to specify the number
411 of desired inodes directly.
413 .BI \-o " creator-os"
414 Overrides the default value of the "creator operating system" field of the
415 filesystem. The creator field is set by default to the name of the OS the
417 executable was compiled for.
419 .B "\-O \fIfeature\fR[,...]"
420 Create a filesystem with the given features (filesystem options),
421 overriding the default filesystem options. The features that are
422 enabled by default are specified by the
424 relation, either in the
431 subsections for the usage types as specified by the
433 option, further modified by the
435 relation found in the
437 subsections for the filesystem and usage types. See the
439 manual page for more details.
440 The filesystem type-specific configuration setting found in the
442 section will override the global default found in
445 The filesystem feature set will be further edited
446 using either the feature set specified by this option,
447 or if this option is not given, by the
449 relation for the filesystem type being created, or in the
451 section of the configuration file.
453 The filesystem feature set is comprised of a list of features, separated
454 by commas, that are to be enabled. To disable a feature, simply
455 prefix the feature name with a caret ('^') character. The
456 pseudo-filesystem feature "none" will clear all filesystem features.
460 Filesystem can contain files that are greater than 2GB. (Modern kernels
461 set this feature automatically when a file > 2GB is created.)
464 Use hashed b-trees to speed up lookups in large directories.
467 Store file type information in directory entries.
470 Allow bitmaps and inode tables for a block group to be placed anywhere
471 on the storage media (use with \-G option to group meta-data in order
472 to create a large virtual block group).
475 Create an ext3 journal (as if using the
480 @JDEV@Create an external ext3 journal on the given device
481 @JDEV@instead of a regular ext2 filesystem.
483 @JDEV@.I external-journal
484 @JDEV@must be created with the same
485 @JDEV@block size as the filesystems that will be using it.
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 Create a filesystem without initializing all of the block groups. This
495 feature also enables checksums and highest-inode-used statistics in each
496 blockgroup. This feature can
497 speed up filesystem creation time noticably (if lazy_itable_init is
498 enabled), and can also reduce
500 time dramatically. It is only supported by the ext4 filesystem in
501 recent Linux kernels.
504 Reserve space so the block group descriptor table may grow in the future.
505 Useful for online resizing using
509 will attempt to reserve enough space so that the
510 filesystem may grow to 1024 times its initial size. This can be changed
516 Create a filesystem with fewer superblock backup copies
517 (saves space on large filesystems).
521 Quiet execution. Useful if
526 Set the filesystem revision for the new filesystem. Note that 1.2
527 kernels only support revision 0 filesystems. The default is to
528 create revision 1 filesystems.
531 Write superblock and group descriptors only. This is useful if all of
532 the superblock and backup superblocks are corrupted, and a last-ditch
533 recovery method is desired. It causes
536 superblock and group descriptors, while not touching the inode table
537 and the block and inode bitmaps. The
539 program should be run immediately after this option is used, and there
540 is no guarantee that any data will be salvageable. It is critical to
541 specify the correct filesystem blocksize when using this option,
542 or there is no chance of recovery.
545 .\" Check the device for bad blocks before creating the file system
546 .\" using the specified test.
550 Specify the filesystem (i.e., ext2, ext3, ext4, etc.) that is to be created.
551 If this option is not specified,
553 will pick a default either via how
554 the command was run (for example, using a name of the form mkfs.ext2,
555 mkfs.ext3, etc.) or via a default as defined by the
556 .BR /etc/mke2fs.conf (5)
559 .BI \-T " usage-type[,...]"
560 Specify how the filesystem is going to be used, so that
562 can choose optimal filesystem parameters for that use. The usage
563 types that are supported are defined in the configuration file
564 .BR /etc/mke2fs.conf (5).
565 The user may specify one or more usage types
566 using a comma separated list.
568 If this option is is not specified,
570 will pick a single default usage type based on the size of the filesystem to
571 be created. If the filesystem size is less than or equal to 3 megabytes,
573 will use the filesystem type
575 If the filesystem size is greater than 3 but less than or equal to
578 will use the filesystem
582 will use the default filesystem type
589 Print the version number of
595 has been written by Theodore Ts'o <tytso@mit.edu>.
600 option but currently ignores it because the second
601 extended file system does not support fragments yet.
603 There may be other ones. Please, report them to the author.
606 is part of the e2fsprogs package and is available from
607 http://e2fsprogs.sourceforge.net.