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mke2fs.8 (25878B)


  1. .\" -*- nroff -*-
  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.
  4. .\"
  5. .TH MKE2FS 8 "Aug 2021" "E2fsprogs version 1.46.4"
  6. .SH NAME
  7. mke2fs \- create an ext2/ext3/ext4 file system
  8. .SH SYNOPSIS
  9. .B mke2fs
  10. [
  11. .B \-c
  12. |
  13. .B \-l
  14. .I filename
  15. ]
  16. [
  17. .B \-b
  18. .I block-size
  19. ]
  20. [
  21. .B \-C
  22. .I cluster-size
  23. ]
  24. [
  25. .B \-d
  26. .I root-directory
  27. ]
  28. [
  29. .B \-D
  30. ]
  31. [
  32. .B \-g
  33. .I blocks-per-group
  34. ]
  35. [
  36. .B \-G
  37. .I number-of-groups
  38. ]
  39. [
  40. .B \-i
  41. .I bytes-per-inode
  42. ]
  43. [
  44. .B \-I
  45. .I inode-size
  46. ]
  47. [
  48. .B \-j
  49. ]
  50. [
  51. .B \-J
  52. .I journal-options
  53. ]
  54. [
  55. .B \-N
  56. .I number-of-inodes
  57. ]
  58. [
  59. .B \-n
  60. ]
  61. [
  62. .B \-m
  63. .I reserved-blocks-percentage
  64. ]
  65. [
  66. .B \-o
  67. .I creator-os
  68. ]
  69. [
  70. .B \-O
  71. [^]\fIfeature\fR[,...]
  72. ]
  73. [
  74. .B \-q
  75. ]
  76. [
  77. .B \-r
  78. .I fs-revision-level
  79. ]
  80. [
  81. .B \-E
  82. .I extended-options
  83. ]
  84. [
  85. .B \-v
  86. ]
  87. [
  88. .B \-F
  89. ]
  90. [
  91. .B \-L
  92. .I volume-label
  93. ]
  94. [
  95. .B \-M
  96. .I last-mounted-directory
  97. ]
  98. [
  99. .B \-S
  100. ]
  101. [
  102. .B \-t
  103. .I fs-type
  104. ]
  105. [
  106. .B \-T
  107. .I usage-type
  108. ]
  109. [
  110. .B \-U
  111. .I UUID
  112. ]
  113. [
  114. .B \-V
  115. ]
  116. [
  117. .B \-e
  118. .I errors-behavior
  119. ]
  120. [
  121. .B \-z
  122. .I undo_file
  123. ]
  124. .I device
  125. [
  126. .I fs-size
  127. ]
  128. .sp
  129. .B "mke2fs \-O journal_dev"
  130. [
  131. .B \-b
  132. .I block-size
  133. ]
  134. .\" No external-journal specific journal options yet (size is ignored)
  135. .\" [
  136. .\" .B \-J
  137. .\" .I journal-options
  138. .\" ]
  139. [
  140. .B \-L
  141. .I volume-label
  142. ]
  143. [
  144. .B \-n
  145. ]
  146. [
  147. .B \-q
  148. ]
  149. [
  150. .B \-v
  151. ]
  152. .I external-journal
  153. [
  154. .I fs-size
  155. ]
  156. .SH DESCRIPTION
  157. .B mke2fs
  158. is used to create an ext2, ext3, or ext4 file system, usually in a disk
  159. partition (or file) named by
  160. .IR device .
  161. .PP
  162. The file system size is specified by
  163. .IR fs-size .
  164. If
  165. .I fs-size
  166. does not have a suffix, it is interpreted as power-of-two kilobytes,
  167. unless the
  168. .B \-b
  169. .I blocksize
  170. option is specified, in which case
  171. .I fs-size
  172. is interpreted as the number of
  173. .I blocksize
  174. blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't'
  175. (either upper-case or lower-case), then it is interpreted in
  176. power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
  177. If
  178. .I fs-size
  179. is omitted,
  180. .B mke2fs
  181. will create the file system based on the device size.
  182. .PP
  183. If
  184. .B mke2fs
  185. is run as
  186. .B mkfs.XXX
  187. (i.e.,
  188. .BR mkfs.ext2 ,
  189. .BR mkfs.ext3 ,
  190. or
  191. .BR mkfs.ext4 )
  192. the option
  193. .B \-t
  194. .I XXX
  195. is implied; so
  196. .B mkfs.ext3
  197. will create a file system for use with ext3,
  198. .B mkfs.ext4
  199. will create a file system for use with ext4, and so on.
  200. .PP
  201. The defaults of the parameters for the newly created file system, if not
  202. overridden by the options listed below, are controlled by the
  203. .B /etc/mke2fs.conf
  204. configuration file. See the
  205. .BR mke2fs.conf (5)
  206. manual page for more details.
  207. .SH OPTIONS
  208. .TP
  209. .BI \-b " block-size"
  210. Specify the size of blocks in bytes. Valid block-size values are powers of two
  211. from 1024 up to 65536 (however note that the kernel is able to mount only
  212. file systems with block-size smaller or equal to the system page size - 4k on
  213. x86 systems, up to 64k on ppc64 or aarch64 depending on kernel configuration).
  214. If omitted, block-size is heuristically determined by the file system size and
  215. the expected usage of the file system (see the
  216. .B \-T
  217. option). In most common cases, the default block size is 4k. If
  218. .I block-size
  219. is preceded by a negative sign ('-'), then
  220. .B mke2fs
  221. will use heuristics to determine the
  222. appropriate block size, with the constraint that the block size will be
  223. at least
  224. .I block-size
  225. bytes. This is useful for certain hardware devices which require that
  226. the blocksize be a multiple of 2k.
  227. .TP
  228. .B \-c
  229. Check the device for bad blocks before creating the file system. If
  230. this option is specified twice, then a slower read-write
  231. test is used instead of a fast read-only test.
  232. .TP
  233. .B \-C " cluster-size"
  234. Specify the size of cluster in bytes for file systems using the bigalloc
  235. feature. Valid cluster-size values are from 2048 to 256M bytes per
  236. cluster. This can only be specified if the bigalloc feature is
  237. enabled. (See the
  238. .B ext4 (5)
  239. man page for more details about bigalloc.) The default cluster size if
  240. bigalloc is enabled is 16 times the block size.
  241. .TP
  242. .BI \-d " root-directory"
  243. Copy the contents of the given directory into the root directory of the
  244. file system.
  245. .TP
  246. .B \-D
  247. Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
  248. lot of buffer cache memory, which may impact other applications running
  249. on a busy server. This option will cause mke2fs to run much more
  250. slowly, however, so there is a tradeoff to using direct I/O.
  251. .TP
  252. .BI \-e " error-behavior"
  253. Change the behavior of the kernel code when errors are detected.
  254. In all cases, a file system error will cause
  255. .BR e2fsck (8)
  256. to check the file system on the next boot.
  257. .I error-behavior
  258. can be one of the following:
  259. .RS 1.2i
  260. .TP 1.2i
  261. .B continue
  262. Continue normal execution.
  263. .TP
  264. .B remount-ro
  265. Remount file system read-only.
  266. .TP
  267. .B panic
  268. Cause a kernel panic.
  269. .RE
  270. .TP
  271. .BI \-E " extended-options"
  272. Set extended options for the file system. Extended options are comma
  273. separated, and may take an argument using the equals ('=') sign. The
  274. .B \-E
  275. option used to be
  276. .B \-R
  277. in earlier versions of
  278. .BR mke2fs .
  279. The
  280. .B \-R
  281. option is still accepted for backwards compatibility, but is deprecated.
  282. The following extended options are supported:
  283. .RS 1.2i
  284. .TP
  285. .BI encoding= encoding-name
  286. Enable the
  287. .I casefold
  288. feature in the super block and set
  289. .I encoding-name
  290. as the encoding to be used. If
  291. .I encoding-name
  292. is not specified, the encoding defined in
  293. .BR mke2fs.conf (5)
  294. is used.
  295. .TP
  296. .BI encoding_flags= encoding-flags
  297. Define parameters for file name character encoding operations. If a
  298. flag is not changed using this parameter, its default value is used.
  299. .I encoding-flags
  300. should be a comma-separated lists of flags to be enabled. To disable a
  301. flag, add it to the list with the prefix "no".
  302. The only flag that can be set right now is
  303. .I strict
  304. which means that invalid strings should be rejected by the file system.
  305. In the default configuration, the
  306. .I strict
  307. flag is disabled.
  308. .TP
  309. .BI mmp_update_interval= interval
  310. Adjust the initial MMP update interval to
  311. .I interval
  312. seconds. Specifying an
  313. .I interval
  314. of 0 means to use the default interval. The specified interval must
  315. be less than 300 seconds. Requires that the
  316. .B mmp
  317. feature be enabled.
  318. .TP
  319. .BI stride= stride-size
  320. Configure the file system for a RAID array with
  321. .I stride-size
  322. file system blocks. This is the number of blocks read or written to disk
  323. before moving to the next disk, which is sometimes referred to as the
  324. .I chunk size.
  325. This mostly affects placement of file system metadata like bitmaps at
  326. .B mke2fs
  327. time to avoid placing them on a single disk, which can hurt performance.
  328. It may also be used by the block allocator.
  329. .TP
  330. .BI stripe_width= stripe-width
  331. Configure the file system for a RAID array with
  332. .I stripe-width
  333. file system blocks per stripe. This is typically stride-size * N, where
  334. N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
  335. parity disk, so N will be the number of disks in the array minus 1).
  336. This allows the block allocator to prevent read-modify-write of the
  337. parity in a RAID stripe if possible when the data is written.
  338. .TP
  339. .BI offset= offset
  340. Create the file system at an offset from the beginning of the device or
  341. file. This can be useful when creating disk images for virtual machines.
  342. .TP
  343. .BI resize= max-online-resize
  344. Reserve enough space so that the block group descriptor table can grow
  345. to support a file system that has
  346. .I max-online-resize
  347. blocks.
  348. .TP
  349. .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
  350. If enabled and the uninit_bg feature is enabled, the inode table will
  351. not be fully initialized by
  352. .BR mke2fs .
  353. This speeds up file system
  354. initialization noticeably, but it requires the kernel to finish
  355. initializing the file system in the background when the file system is
  356. first mounted. If the option value is omitted, it defaults to 1 to
  357. enable lazy inode table zeroing.
  358. .TP
  359. .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
  360. If enabled, the journal inode will not be fully zeroed out by
  361. .BR mke2fs .
  362. This speeds up file system initialization noticeably, but carries some
  363. small risk if the system crashes before the journal has been overwritten
  364. entirely one time. If the option value is omitted, it defaults to 1 to
  365. enable lazy journal inode zeroing.
  366. .TP
  367. .B no_copy_xattrs
  368. Normally
  369. .B mke2fs
  370. will copy the extended attributes of the files in the directory
  371. hierarchy specified via the (optional)
  372. .B \-d
  373. option. This will disable the copy and leaves the files in the newly
  374. created file system without any extended attributes.
  375. .TP
  376. .BI num_backup_sb= <0|1|2>
  377. If the
  378. .B sparse_super2
  379. file system feature is enabled this option controls whether there will
  380. be 0, 1, or 2 backup superblocks created in the file system.
  381. .TP
  382. .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
  383. Place the allocation bitmaps and the inode table at the beginning of the
  384. disk. This option requires that the flex_bg file system feature to be
  385. enabled in order for it to have effect, and will also create the journal
  386. at the beginning of the file system. This option is useful for flash
  387. devices that use SLC flash at the beginning of the disk.
  388. It also maximizes the range of contiguous data blocks, which
  389. can be useful for certain specialized use cases, such as supported
  390. Shingled Drives.
  391. .TP
  392. .BI root_owner [=uid:gid]
  393. Specify the numeric user and group ID of the root directory. If no UID:GID
  394. is specified, use the user and group ID of the user running \fBmke2fs\fR.
  395. In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
  396. set by default to the UID and GID of the user running the mke2fs command.
  397. The \fBroot_owner=\fR option allows explicitly specifying these values,
  398. and avoid side-effects for users that do not expect the contents of the
  399. file system to change based on the user running \fBmke2fs\fR.
  400. .TP
  401. .B test_fs
  402. Set a flag in the file system superblock indicating that it may be
  403. mounted using experimental kernel code, such as the ext4dev file system.
  404. .TP
  405. .B discard
  406. Attempt to discard blocks at mkfs time (discarding blocks initially is useful
  407. on solid state devices and sparse / thin-provisioned storage). When the device
  408. advertises that discard also zeroes data (any subsequent read after the discard
  409. and before write returns zero), then mark all not-yet-zeroed inode tables as
  410. zeroed. This significantly speeds up file system initialization. This is set
  411. as default.
  412. .TP
  413. .B nodiscard
  414. Do not attempt to discard blocks at mkfs time.
  415. .TP
  416. .B quotatype
  417. Specify the which quota types (usrquota, grpquota, prjquota) which
  418. should be enabled in the created file system. The argument of this
  419. extended option should be a colon separated list. This option has
  420. effect only if the
  421. .B quota
  422. feature is set. The default quota types to be initialized if this
  423. option is not specified is both user and group quotas. If the project
  424. feature is enabled that project quotas will be initialized as well.
  425. .RE
  426. .TP
  427. .B \-F
  428. Force
  429. .B mke2fs
  430. to create a file system, even if the specified device is not a partition
  431. on a block special device, or if other parameters do not make sense.
  432. In order to force
  433. .B mke2fs
  434. to create a file system even if the file system appears to be in use
  435. or is mounted (a truly dangerous thing to do), this option must be
  436. specified twice.
  437. .TP
  438. .BI \-g " blocks-per-group"
  439. Specify the number of blocks in a block group. There is generally no
  440. reason for the user to ever set this parameter, as the default is optimal
  441. for the file system. (For administrators who are creating
  442. file systems on RAID arrays, it is preferable to use the
  443. .I stride
  444. RAID parameter as part of the
  445. .B \-E
  446. option rather than manipulating the number of blocks per group.)
  447. This option is generally used by developers who
  448. are developing test cases.
  449. .IP
  450. If the bigalloc feature is enabled, the
  451. .B \-g
  452. option will specify the number of clusters in a block group.
  453. .TP
  454. .BI \-G " number-of-groups"
  455. Specify the number of block groups that will be packed together to
  456. create a larger virtual block group (or "flex_bg group") in an
  457. ext4 file system. This improves meta-data locality and performance
  458. on meta-data heavy workloads. The number of groups must be a power
  459. of 2 and may only be specified if the
  460. .B flex_bg
  461. file system feature is enabled.
  462. .TP
  463. .BI \-i " bytes-per-inode"
  464. Specify the bytes/inode ratio.
  465. .B mke2fs
  466. creates an inode for every
  467. .I bytes-per-inode
  468. bytes of space on the disk. The larger the
  469. .I bytes-per-inode
  470. ratio, the fewer inodes will be created. This value generally shouldn't
  471. be smaller than the blocksize of the file system, since in that case more
  472. inodes would be made than can ever be used. Be warned that it is not
  473. possible to change this ratio on a file system after it is created, so be
  474. careful deciding the correct value for this parameter. Note that resizing
  475. a file system changes the number of inodes to maintain this ratio.
  476. .TP
  477. .BI \-I " inode-size"
  478. Specify the size of each inode in bytes.
  479. The
  480. .I inode-size
  481. value must be a power of 2 larger or equal to 128. The larger the
  482. .I inode-size
  483. the more space the inode table will consume, and this reduces the usable
  484. space in the file system and can also negatively impact performance.
  485. It is not
  486. possible to change this value after the file system is created.
  487. .IP
  488. File systems with an inode size of 128 bytes do not support timestamps
  489. beyond January 19, 2038. Inodes which are 256 bytes or larger will
  490. support extended timestamps, project id's, and the ability to store some
  491. extended attributes in the inode table for improved performance.
  492. .IP
  493. The default inode size is controlled by the
  494. .BR mke2fs.conf (5)
  495. file. In the
  496. .B mke2fs.conf
  497. file shipped with e2fsprogs, the default inode size is 256 bytes for
  498. most file systems, except for small file systems where the inode size
  499. will be 128 bytes.
  500. .TP
  501. .B \-j
  502. Create the file system with an ext3 journal. If the
  503. .B \-J
  504. option is not specified, the default journal parameters will be used to
  505. create an appropriately sized journal (given the size of the file system)
  506. stored within the file system. Note that you must be using a kernel
  507. which has ext3 support in order to actually make use of the journal.
  508. .TP
  509. .BI \-J " journal-options"
  510. Create the ext3 journal using options specified on the command-line.
  511. Journal options are comma
  512. separated, and may take an argument using the equals ('=') sign.
  513. The following journal options are supported:
  514. .RS 1.2i
  515. .TP
  516. .BI size= journal-size
  517. Create an internal journal (i.e., stored inside the file system) of size
  518. .I journal-size
  519. megabytes.
  520. The size of the journal must be at least 1024 file system blocks
  521. (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
  522. and may be no more than 10,240,000 file system blocks or half the total
  523. file system size (whichever is smaller)
  524. .TP
  525. .BI fast_commit_size= fast-commit-size
  526. Create an additional fast commit journal area of size
  527. .I fast-commit-size
  528. kilobytes.
  529. This option is only valid if
  530. .B fast_commit
  531. feature is enabled
  532. on the file system. If this option is not specified and if
  533. .B fast_commit
  534. feature is turned on, fast commit area size defaults to
  535. .I journal-size
  536. / 64 megabytes. The total size of the journal with
  537. .B fast_commit
  538. feature set is
  539. .I journal-size
  540. + (
  541. .I fast-commit-size
  542. * 1024) megabytes. The total journal size may be no more than
  543. 10,240,000 file system blocks or half the total file system size
  544. (whichever is smaller).
  545. .TP
  546. .BI location =journal-location
  547. Specify the location of the journal. The argument
  548. .I journal-location
  549. can either be specified as a block number, or if the number has a units
  550. suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
  551. beginning of the file system.
  552. .TP
  553. .BI device= external-journal
  554. Attach the file system to the journal block device located on
  555. .IR external-journal .
  556. The external
  557. journal must already have been created using the command
  558. .IP
  559. .B mke2fs -O journal_dev
  560. .I external-journal
  561. .IP
  562. Note that
  563. .I external-journal
  564. must have been created with the
  565. same block size as the new file system.
  566. In addition, while there is support for attaching
  567. multiple file systems to a single external journal,
  568. the Linux kernel and
  569. .BR e2fsck (8)
  570. do not currently support shared external journals yet.
  571. .IP
  572. Instead of specifying a device name directly,
  573. .I external-journal
  574. can also be specified by either
  575. .BI LABEL= label
  576. or
  577. .BI UUID= UUID
  578. to locate the external journal by either the volume label or UUID
  579. stored in the ext2 superblock at the start of the journal. Use
  580. .BR dumpe2fs (8)
  581. to display a journal device's volume label and UUID. See also the
  582. .B -L
  583. option of
  584. .BR tune2fs (8).
  585. .RE
  586. .IP
  587. Only one of the
  588. .BR size " or " device
  589. options can be given for a file system.
  590. .TP
  591. .BI \-l " filename"
  592. Read the bad blocks list from
  593. .IR filename .
  594. Note that the block numbers in the bad block list must be generated
  595. using the same block size as used by
  596. .BR mke2fs .
  597. As a result, the
  598. .B \-c
  599. option to
  600. .B mke2fs
  601. is a much simpler and less error-prone method of checking a disk for bad
  602. blocks before formatting it, as
  603. .B mke2fs
  604. will automatically pass the correct parameters to the
  605. .B badblocks
  606. program.
  607. .TP
  608. .BI \-L " new-volume-label"
  609. Set the volume label for the file system to
  610. .IR new-volume-label .
  611. The maximum length of the
  612. volume label is 16 bytes.
  613. .TP
  614. .BI \-m " reserved-blocks-percentage"
  615. Specify the percentage of the file system blocks reserved for
  616. the super-user. This avoids fragmentation, and allows root-owned
  617. daemons, such as
  618. .BR syslogd (8),
  619. to continue to function correctly after non-privileged processes are
  620. prevented from writing to the file system. The default percentage
  621. is 5%.
  622. .TP
  623. .BI \-M " last-mounted-directory"
  624. Set the last mounted directory for the file system. This might be useful
  625. for the sake of utilities that key off of the last mounted directory to
  626. determine where the file system should be mounted.
  627. .TP
  628. .B \-n
  629. Causes
  630. .B mke2fs
  631. to not actually create a file system, but display what it
  632. would do if it were to create a file system. This can be used to
  633. determine the location of the backup superblocks for a particular
  634. file system, so long as the
  635. .B mke2fs
  636. parameters that were passed when the
  637. file system was originally created are used again. (With the
  638. .B \-n
  639. option added, of course!)
  640. .TP
  641. .BI \-N " number-of-inodes"
  642. Overrides the default calculation of the number of inodes that should be
  643. reserved for the file system (which is based on the number of blocks and
  644. the
  645. .I bytes-per-inode
  646. ratio). This allows the user to specify the number
  647. of desired inodes directly.
  648. .TP
  649. .BI \-o " creator-os"
  650. Overrides the default value of the "creator operating system" field of the
  651. file system. The creator field is set by default to the name of the OS the
  652. .B mke2fs
  653. executable was compiled for.
  654. .TP
  655. .B "\-O \fR[^]\fIfeature\fR[,...]"
  656. Create a file system with the given features (file system options),
  657. overriding the default file system options. The features that are
  658. enabled by default are specified by the
  659. .I base_features
  660. relation, either in the
  661. .I [defaults]
  662. section in the
  663. .B /etc/mke2fs.conf
  664. configuration file,
  665. or in the
  666. .I [fs_types]
  667. subsections for the usage types as specified by the
  668. .B \-T
  669. option, further modified by the
  670. .I features
  671. relation found in the
  672. .I [fs_types]
  673. subsections for the file system and usage types. See the
  674. .BR mke2fs.conf (5)
  675. manual page for more details.
  676. The file system type-specific configuration setting found in the
  677. .I [fs_types]
  678. section will override the global default found in
  679. .IR [defaults] .
  680. .sp
  681. The file system feature set will be further edited
  682. using either the feature set specified by this option,
  683. or if this option is not given, by the
  684. .I default_features
  685. relation for the file system type being created, or in the
  686. .I [defaults]
  687. section of the configuration file.
  688. .sp
  689. The file system feature set is comprised of a list of features, separated
  690. by commas, that are to be enabled. To disable a feature, simply
  691. prefix the feature name with a caret ('^') character.
  692. Features with dependencies will not be removed successfully.
  693. The pseudo-file system feature "none" will clear all file system features.
  694. .TP
  695. For more information about the features which can be set, please see
  696. the manual page
  697. .BR ext4 (5).
  698. .TP
  699. .B \-q
  700. Quiet execution. Useful if
  701. .B mke2fs
  702. is run in a script.
  703. .TP
  704. .BI \-r " revision"
  705. Set the file system revision for the new file system. Note that 1.2
  706. kernels only support revision 0 file systems. The default is to
  707. create revision 1 file systems.
  708. .TP
  709. .B \-S
  710. Write superblock and group descriptors only. This is an extreme
  711. measure to be taken only in the very unlikely case that all of
  712. the superblock and backup superblocks are corrupted, and a last-ditch
  713. recovery method is desired by experienced users. It causes
  714. .B mke2fs
  715. to reinitialize the superblock and group descriptors, while not
  716. touching the inode table and the block and inode bitmaps. The
  717. .B e2fsck
  718. program should be run immediately after this option is used, and there
  719. is no guarantee that any data will be salvageable. Due to the wide
  720. variety of possible options to
  721. .B mke2fs
  722. that affect the on-disk layout, it is critical to specify exactly
  723. the same format options, such as blocksize, fs-type, feature flags, and
  724. other tunables when using this option, or the file system will be further
  725. corrupted. In some cases, such as file systems that have been resized,
  726. or have had features enabled after format time, it is impossible to
  727. overwrite all of the superblocks correctly, and at least some file system
  728. corruption will occur. It is best to run this on a full copy of the
  729. file system so other options can be tried if this doesn't work.
  730. .\" .TP
  731. .\" .BI \-t " test"
  732. .\" Check the device for bad blocks before creating the file system
  733. .\" using the specified test.
  734. .TP
  735. .BI \-t " fs-type"
  736. Specify the file system type (i.e., ext2, ext3, ext4, etc.) that is
  737. to be created.
  738. If this option is not specified,
  739. .B mke2fs
  740. will pick a default either via how
  741. the command was run (for example, using a name of the form mkfs.ext2,
  742. mkfs.ext3, etc.) or via a default as defined by the
  743. .B /etc/mke2fs.conf
  744. file. This option controls which file system options are used by
  745. default, based on the
  746. .B fstypes
  747. configuration stanza in
  748. .BR /etc/mke2fs.conf .
  749. .sp
  750. If the
  751. .B \-O
  752. option is used to explicitly add or remove file system options that
  753. should be set in the newly created file system, the
  754. resulting file system may not be supported by the requested
  755. .IR fs-type .
  756. (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
  757. file system that is not supported by the ext3 implementation as found in
  758. the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
  759. will create a file system that does not have a journal and hence will not
  760. be supported by the ext3 file system code in the Linux kernel.)
  761. .TP
  762. .BI \-T " usage-type[,...]"
  763. Specify how the file system is going to be used, so that
  764. .B mke2fs
  765. can choose optimal file system parameters for that use. The usage
  766. types that are supported are defined in the configuration file
  767. .BR /etc/mke2fs.conf .
  768. The user may specify one or more usage types
  769. using a comma separated list.
  770. .sp
  771. If this option is is not specified,
  772. .B mke2fs
  773. will pick a single default usage type based on the size of the file system to
  774. be created. If the file system size is less than 3 megabytes,
  775. .B mke2fs
  776. will use the file system type
  777. .IR floppy .
  778. If the file system size is greater than or equal to 3 but less than
  779. 512 megabytes,
  780. .BR mke2fs (8)
  781. will use the file system type
  782. .IR small .
  783. If the file system size is greater than or equal to 4 terabytes but less than
  784. 16 terabytes,
  785. .BR mke2fs (8)
  786. will use the file system type
  787. .IR big .
  788. If the file system size is greater than or equal to 16 terabytes,
  789. .BR mke2fs (8)
  790. will use the file system type
  791. .IR huge .
  792. Otherwise,
  793. .BR mke2fs (8)
  794. will use the default file system type
  795. .IR default .
  796. .TP
  797. .BI \-U " UUID"
  798. Set the universally unique identifier (UUID) of the file system to
  799. .IR UUID .
  800. The format of the UUID is a series of hex digits separated by hyphens,
  801. like this:
  802. "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
  803. The
  804. .I UUID
  805. parameter may also be one of the following:
  806. .RS 1.2i
  807. .TP
  808. .I clear
  809. clear the file system UUID
  810. .TP
  811. .I random
  812. generate a new randomly-generated UUID
  813. .TP
  814. .I time
  815. generate a new time-based UUID
  816. .RE
  817. .TP
  818. .B \-v
  819. Verbose execution.
  820. .TP
  821. .B \-V
  822. Print the version number of
  823. .B mke2fs
  824. and exit.
  825. .TP
  826. .BI \-z " undo_file"
  827. Before overwriting a file system block, write the old contents of the block to
  828. an undo file. This undo file can be used with e2undo(8) to restore the old
  829. contents of the file system should something go wrong. If the empty string is
  830. passed as the undo_file argument, the undo file will be written to a file named
  831. mke2fs-\fIdevice\fR.e2undo in the directory specified via the
  832. \fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
  833. in the configuration file.
  834. WARNING: The undo file cannot be used to recover from a power or system crash.
  835. .SH ENVIRONMENT
  836. .TP
  837. .B MKE2FS_SYNC
  838. If set to non-zero integer value, its value is used to determine how often
  839. .BR sync (2)
  840. is called during inode table initialization.
  841. .TP
  842. .B MKE2FS_CONFIG
  843. Determines the location of the configuration file (see
  844. .BR mke2fs.conf (5)).
  845. .TP
  846. .B MKE2FS_FIRST_META_BG
  847. If set to non-zero integer value, its value is used to determine first meta
  848. block group. This is mostly for debugging purposes.
  849. .TP
  850. .B MKE2FS_DEVICE_SECTSIZE
  851. If set to non-zero integer value, its value is used to determine logical
  852. sector size of the
  853. .IR device .
  854. .TP
  855. .B MKE2FS_DEVICE_PHYS_SECTSIZE
  856. If set to non-zero integer value, its value is used to determine physical
  857. sector size of the
  858. .IR device .
  859. .TP
  860. .B MKE2FS_SKIP_CHECK_MSG
  861. If set, do not show the message of file system automatic check caused by
  862. mount count or check interval.
  863. .SH AUTHOR
  864. This version of
  865. .B mke2fs
  866. has been written by Theodore Ts'o <tytso@mit.edu>.
  867. .SH AVAILABILITY
  868. .B mke2fs
  869. is part of the e2fsprogs package and is available from
  870. http://e2fsprogs.sourceforge.net.
  871. .SH SEE ALSO
  872. .BR mke2fs.conf (5),
  873. .BR badblocks (8),
  874. .BR dumpe2fs (8),
  875. .BR e2fsck (8),
  876. .BR tune2fs (8),
  877. .BR ext4 (5)