misc/mke2fs.8.in

   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 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
   6 .SH NAME
   7 mke2fs \- create an ext2/ext3/ext4 filesystem
   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 \-D
  22 ]
  23 [
  24 .B \-f
  25 .I fragment-size
  26 ]
  27 [
  28 .B \-g
  29 .I blocks-per-group
  30 ]
  31 [
  32 .B \-G
  33 .I number-of-groups
  34 ]
  35 [
  36 .B \-i
  37 .I bytes-per-inode
  38 ]
  39 [
  40 .B \-I
  41 .I inode-size
  42 ]
  43 [
  44 .B \-j
  45 ]
  46 [
  47 .B \-J
  48 .I journal-options
  49 ]
  50 [
  51 .B \-N
  52 .I number-of-inodes
  53 ]
  54 [
  55 .B \-d
  56 .I root-directory
  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 .I device
 121 [
 122 .I fs-size
 123 ]
 124 @JDEV@.sp
 125 @JDEV@.B "mke2fs \-O journal_dev"
 126 @JDEV@[
 127 @JDEV@.B \-b
 128 @JDEV@.I block-size
 129 @JDEV@]
 130 .\" No external-journal specific journal options yet (size is ignored)
 131 .\" @JDEV@[
 132 .\" @JDEV@.B \-J
 133 .\" @JDEV@.I journal-options
 134 .\" @JDEV@]
 135 @JDEV@[
 136 @JDEV@.B \-L
 137 @JDEV@.I volume-label
 138 @JDEV@]
 139 @JDEV@[
 140 @JDEV@.B \-n
 141 @JDEV@]
 142 @JDEV@[
 143 @JDEV@.B \-q
 144 @JDEV@]
 145 @JDEV@[
 146 @JDEV@.B \-v
 147 @JDEV@]
 148 @JDEV@.I external-journal
 149 @JDEV@[
 150 @JDEV@.I fs-size
 151 @JDEV@]
 152 .SH DESCRIPTION
 153 .B mke2fs
 154 is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
 155 partition (or file) named by
 156 .IR device .
 157 .PP
 158 The file system size is specified by
 159 .IR fs-size .
 160 If
 161 .I fs-size
 162 does not have a suffix, it is interpreted as power-of-two kilobytes,
 163 unless the
 164 .B \-b
 165 .I blocksize
 166 option is specified, in which case
 167 .I fs-size
 168 is interpreted as the number of
 169 .I blocksize
 170 blocks.   If the fs-size is suffixed by 'k', 'm', 'g', 't'
 171 (either upper-case or lower-case), then it is interpreted in
 172 power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
 173 If
 174 .I fs-size
 175 is omitted,
 176 .B mke2fs
 177 will create the file system based on the device size.
 178 .PP
 179 If
 180 .B mke2fs
 181 is run as
 182 .B mkfs.XXX
 183 (i.e.,
 184 .BR mkfs.ext2 ,
 185 .BR mkfs.ext3 ,
 186 or
 187 .BR mkfs.ext4 )
 188 the option
 189 .B \-t
 190 .I XXX
 191 is implied; so
 192 .B mkfs.ext3
 193 will create a file system for use with ext3,
 194 .B mkfs.ext4
 195 will create a file system for use with ext4, and so on.
 196 .PP
 197 The defaults of the parameters for the newly created filesystem, if not
 198 overridden by the options listed below, are controlled by the
 199 .B /etc/mke2fs.conf
 200 configuration file.  See the
 201 .BR mke2fs.conf (5)
 202 manual page for more details.
 203 .SH OPTIONS
 204 .TP
 205 .BI \-b " block-size"
 206 Specify the size of blocks in bytes.  Valid block-size values are 1024,
 207 2048 and 4096 bytes per block.  If omitted,
 208 block-size is heuristically determined by the filesystem size and
 209 the expected usage of the filesystem (see the
 210 .B \-T
 211 option).  If
 212 .I block-size
 213 is preceded by a negative sign ('-'), then
 214 .B mke2fs
 215 will use heuristics to determine the
 216 appropriate block size, with the constraint that the block size will be
 217 at least
 218 .I block-size
 219 bytes.  This is useful for certain hardware devices which require that
 220 the blocksize be a multiple of 2k.
 221 .TP
 222 .B \-c
 223 Check the device for bad blocks before creating the file system.  If
 224 this option is specified twice, then a slower read-write
 225 test is used instead of a fast read-only test.
 226 .TP
 227 .B \-C " cluster-size"
 228 Specify the size of cluster in bytes for filesystems using the bigalloc
 229 feature.  Valid cluster-size values are from 2048 to 256M bytes per
 230 cluster.  This can only be specified if the bigalloc feature is
 231 enabled.  (See the
 232 .B ext4 (5)
 233 man page for more details about bigalloc.)   The default cluster size if
 234 bigalloc is enabled is 16 times the block size.
 235 .TP
 236 .B \-D
 237 Use direct I/O when writing to the disk.  This avoids mke2fs dirtying a
 238 lot of buffer cache memory, which may impact other applications running
 239 on a busy server.  This option will cause mke2fs to run much more
 240 slowly, however, so there is a tradeoff to using direct I/O.
 241 .TP
 242 .BI \-e " error-behavior"
 243 Change the behavior of the kernel code when errors are detected.
 244 In all cases, a filesystem error will cause
 245 .BR e2fsck (8)
 246 to check the filesystem on the next boot.
 247 .I error-behavior
 248 can be one of the following:
 249 .RS 1.2i
 250 .TP 1.2i
 251 .B continue
 252 Continue normal execution.
 253 .TP
 254 .B remount-ro
 255 Remount filesystem read-only.
 256 .TP
 257 .B panic
 258 Cause a kernel panic.
 259 .RE
 260 .TP
 261 .BI \-E " extended-options"
 262 Set extended options for the filesystem.  Extended options are comma
 263 separated, and may take an argument using the equals ('=') sign.  The
 264 .B \-E
 265 option used to be
 266 .B \-R
 267 in earlier versions of
 268 .BR mke2fs .
 269 The
 270 .B \-R
 271 option is still accepted for backwards compatibility, but is deprecated.
 272 The following extended options are supported:
 273 .RS 1.2i
 274 .TP
 275 .BI mmp_update_interval= interval
 276 Adjust the initial MMP update interval to
 277 .I interval
 278 seconds.  Specifying an
 279 .I interval
 280 of 0 means to use the default interval.  The specified interval must
 281 be less than 300 seconds.  Requires that the
 282 .B mmp
 283 feature be enabled.
 284 .TP
 285 .BI stride= stride-size
 286 Configure the filesystem for a RAID array with
 287 .I stride-size
 288 filesystem blocks. This is the number of blocks read or written to disk
 289 before moving to the next disk, which is sometimes referred to as the
 290 .I chunk size.
 291 This mostly affects placement of filesystem metadata like bitmaps at
 292 .B mke2fs
 293 time to avoid placing them on a single disk, which can hurt performance.
 294 It may also be used by the block allocator.
 295 .TP
 296 .BI stripe_width= stripe-width
 297 Configure the filesystem for a RAID array with
 298 .I stripe-width
 299 filesystem blocks per stripe. This is typically stride-size * N, where
 300 N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
 301 parity disk, so N will be the number of disks in the array minus 1).
 302 This allows the block allocator to prevent read-modify-write of the
 303 parity in a RAID stripe if possible when the data is written.
 304 .TP
 305 .BI offset= offset
 306 Create the filesystem at an offset from the beginning of the device or
 307 file.  This can be useful when creating disk images for virtual machines.
 308 .TP
 309 .BI resize= max-online-resize
 310 Reserve enough space so that the block group descriptor table can grow
 311 to support a filesystem that has
 312 .I max-online-resize
 313 blocks.
 314 .TP
 315 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
 316 If enabled and the uninit_bg feature is enabled, the inode table will
 317 not be fully initialized by
 318 .BR mke2fs .
 319 This speeds up filesystem
 320 initialization noticeably, but it requires the kernel to finish
 321 initializing the filesystem in the background when the filesystem is
 322 first mounted.  If the option value is omitted, it defaults to 1 to
 323 enable lazy inode table zeroing.
 324 .TP
 325 .B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
 326 If enabled, the journal inode will not be fully zeroed out by
 327 .BR mke2fs .
 328 This speeds up filesystem initialization noticeably, but carries some
 329 small risk if the system crashes before the journal has been overwritten
 330 entirely one time.  If the option value is omitted, it defaults to 1 to
 331 enable lazy journal inode zeroing.
 332 .TP
 333 .BI num_backup_sb= <0|1|2>
 334 If the
 335 .B sparse_super2
 336 file system feature is enabled this option controls whether there will
 337 be 0, 1, or 2 backup superblocks created in the file system.
 338 .TP
 339 .B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
 340 Place the allocation bitmaps and the inode table at the beginning of the
 341 disk.  This option requires that the flex_bg file system feature to be
 342 enabled in order for it to have effect, and will also create the journal
 343 at the beginning of the file system.  This option is useful for flash
 344 devices that use SLC flash at the beginning of the disk.
 345 It also maximizes the range of contiguous data blocks, which
 346 can be useful for certain specialized use cases, such as supported
 347 Shingled Drives.
 348 .TP
 349 .BI root_owner [=uid:gid]
 350 Specify the numeric user and group ID of the root directory.  If no UID:GID
 351 is specified, use the user and group ID of the user running \fBmke2fs\fR.
 352 In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
 353 set by default to the UID and GID of the user running the mke2fs command.
 354 The \fBroot_owner=\fR option allows explicitly specifying these values,
 355 and avoid side-effects for users that do not expect the contents of the
 356 filesystem to change based on the user running \fBmke2fs\fR.
 357 .TP
 358 .B test_fs
 359 Set a flag in the filesystem superblock indicating that it may be
 360 mounted using experimental kernel code, such as the ext4dev filesystem.
 361 .TP
 362 .BI discard
 363 Attempt to discard blocks at mkfs time (discarding blocks initially is useful
 364 on solid state devices and sparse / thin-provisioned storage). When the device
 365 advertises that discard also zeroes data (any subsequent read after the discard
 366 and before write returns zero), then mark all not-yet-zeroed inode tables as
 367 zeroed. This significantly speeds up filesystem initialization. This is set
 368 as default.
 369 .TP
 370 .BI nodiscard
 371 Do not attempt to discard blocks at mkfs time.
 372 @QUOTA_MAN_COMMENT@.TP
 373 @QUOTA_MAN_COMMENT@.BI quotatype
 374 @QUOTA_MAN_COMMENT@Specify which quota type ('usr' or 'grp') is to be
 375 @QUOTA_MAN_COMMENT@initialized. This option has effect only if the
 376 @QUOTA_MAN_COMMENT@.B quota
 377 @QUOTA_MAN_COMMENT@feature is set. Without this extended option, the default
 378 @QUOTA_MAN_COMMENT@behavior is to initialize both user and group quotas.
 379 .RE
 380 .TP
 381 .BI \-f " fragment-size"
 382 Specify the size of fragments in bytes.
 383 .TP
 384 .B \-F
 385 Force
 386 .B mke2fs
 387 to create a filesystem, even if the specified device is not a partition
 388 on a block special device, or if other parameters do not make sense.
 389 In order to force
 390 .B mke2fs
 391 to create a filesystem even if the filesystem appears to be in use
 392 or is mounted (a truly dangerous thing to do), this option must be
 393 specified twice.
 394 .TP
 395 .BI \-g " blocks-per-group"
 396 Specify the number of blocks in a block group.  There is generally no
 397 reason for the user to ever set this parameter, as the default is optimal
 398 for the filesystem.  (For administrators who are creating
 399 filesystems on RAID arrays, it is preferable to use the
 400 .I stride
 401 RAID parameter as part of the
 402 .B \-E
 403 option rather than manipulating the number of blocks per group.)
 404 This option is generally used by developers who
 405 are developing test cases.
 406 .IP
 407 If the bigalloc feature is enabled, the
 408 .B \-g
 409 option will specify the number of clusters in a block group.
 410 .TP
 411 .BI \-G " number-of-groups"
 412 Specify the number of block groups that will be packed together to
 413 create a larger virtual block group (or "flex_bg group") in an
 414 ext4 filesystem.  This improves meta-data locality and performance
 415 on meta-data heavy workloads.  The number of groups must be a power
 416 of 2 and may only be specified if the
 417 .B flex_bg
 418 filesystem feature is enabled.
 419 .TP
 420 .BI \-i " bytes-per-inode"
 421 Specify the bytes/inode ratio.
 422 .B mke2fs
 423 creates an inode for every
 424 .I bytes-per-inode
 425 bytes of space on the disk.  The larger the
 426 .I bytes-per-inode
 427 ratio, the fewer inodes will be created.  This value generally shouldn't
 428 be smaller than the blocksize of the filesystem, since in that case more
 429 inodes would be made than can ever be used.  Be warned that it is not
 430 possible to change this ratio on a filesystem after it is created, so be
 431 careful deciding the correct value for this parameter.  Note that resizing
 432 a filesystem changes the numer of inodes to maintain this ratio.
 433 .TP
 434 .BI \-I " inode-size"
 435 Specify the size of each inode in bytes.
 436 The
 437 .I inode-size
 438 value must be a power of 2 larger or equal to 128.  The larger the
 439 .I inode-size
 440 the more space the inode table will consume, and this reduces the usable
 441 space in the filesystem and can also negatively impact performance.
 442 It is not
 443 possible to change this value after the filesystem is created.
 444 .IP
 445 In kernels after 2.6.10 and some
 446 earlier vendor kernels it is possible to utilize inodes larger than
 447 128 bytes to store
 448 extended attributes for improved performance.
 449 Extended attributes
 450 stored in large inodes are not visible with older kernels, and such
 451 filesystems will not be mountable with 2.4 kernels at all.
 452 .IP
 453 The default inode size is controlled by the
 454 .BR mke2fs.conf (5)
 455 file.  In the
 456 .B mke2fs.conf
 457 file shipped with e2fsprogs, the default inode size is 256 bytes for
 458 most file systems, except for small file systems where the inode size
 459 will be 128 bytes.
 460 .TP
 461 .B \-j
 462 Create the filesystem with an ext3 journal.  If the
 463 .B \-J
 464 option is not specified, the default journal parameters will be used to
 465 create an appropriately sized journal (given the size of the filesystem)
 466 stored within the filesystem.  Note that you must be using a kernel
 467 which has ext3 support in order to actually make use of the journal.
 468 .TP
 469 .BI \-J " journal-options"
 470 Create the ext3 journal using options specified on the command-line.
 471 Journal options are comma
 472 separated, and may take an argument using the equals ('=')  sign.
 473 The following journal options are supported:
 474 .RS 1.2i
 475 .TP
 476 .BI size= journal-size
 477 Create an internal journal (i.e., stored inside the filesystem) of size
 478 .I journal-size
 479 megabytes.
 480 The size of the journal must be at least 1024 filesystem blocks
 481 (i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
 482 and may be no more than 10,240,000 filesystem blocks or half the total
 483 file system size (whichever is smaller)
 484 .TP
 485 .BI location =journal-location
 486 Specify the location of the journal.  The argument
 487 .I journal-location
 488 can either be specified as a block number, or if the number has a units
 489 suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
 490 beginning of the file system.
 491 @JDEV@.TP
 492 @JDEV@.BI device= external-journal
 493 @JDEV@Attach the filesystem to the journal block device located on
 494 @JDEV@.IR external-journal .
 495 @JDEV@The external
 496 @JDEV@journal must already have been created using the command
 497 @JDEV@.IP
 498 @JDEV@.B mke2fs -O journal_dev
 499 @JDEV@.I external-journal
 500 @JDEV@.IP
 501 @JDEV@Note that
 502 @JDEV@.I external-journal
 503 @JDEV@must have been created with the
 504 @JDEV@same block size as the new filesystem.
 505 @JDEV@In addition, while there is support for attaching
 506 @JDEV@multiple filesystems to a single external journal,
 507 @JDEV@the Linux kernel and
 508 @JDEV@.BR e2fsck (8)
 509 @JDEV@do not currently support shared external journals yet.
 510 @JDEV@.IP
 511 @JDEV@Instead of specifying a device name directly,
 512 @JDEV@.I external-journal
 513 @JDEV@can also be specified by either
 514 @JDEV@.BI LABEL= label
 515 @JDEV@or
 516 @JDEV@.BI UUID= UUID
 517 @JDEV@to locate the external journal by either the volume label or UUID
 518 @JDEV@stored in the ext2 superblock at the start of the journal.  Use
 519 @JDEV@.BR dumpe2fs (8)
 520 @JDEV@to display a journal device's volume label and UUID.  See also the
 521 @JDEV@.B -L
 522 @JDEV@option of
 523 @JDEV@.BR tune2fs (8).
 524 .RE
 525 @JDEV@.IP
 526 @JDEV@Only one of the
 527 @JDEV@.BR size " or " device
 528 @JDEV@options can be given for a filesystem.
 529 .TP
 530 .BI \-l " filename"
 531 Read the bad blocks list from
 532 .IR filename .
 533 Note that the block numbers in the bad block list must be generated
 534 using the same block size as used by
 535 .BR mke2fs .
 536 As a result, the
 537 .B \-c
 538 option to
 539 .B mke2fs
 540 is a much simpler and less error-prone method of checking a disk for bad
 541 blocks before formatting it, as
 542 .B mke2fs
 543 will automatically pass the correct parameters to the
 544 .B badblocks
 545 program.
 546 .TP
 547 .BI \-L " new-volume-label"
 548 Set the volume label for the filesystem to
 549 .IR new-volume-label .
 550 The maximum length of the
 551 volume label is 16 bytes.
 552 .TP
 553 .BI \-m " reserved-blocks-percentage"
 554 Specify the percentage of the filesystem blocks reserved for
 555 the super-user.  This avoids fragmentation, and allows root-owned
 556 daemons, such as
 557 .BR syslogd (8),
 558 to continue to function correctly after non-privileged processes are
 559 prevented from writing to the filesystem.  The default percentage
 560 is 5%.
 561 .TP
 562 .BI \-M " last-mounted-directory"
 563 Set the last mounted directory for the filesystem.  This might be useful
 564 for the sake of utilities that key off of the last mounted directory to
 565 determine where the filesystem should be mounted.
 566 .TP
 567 .B \-n
 568 Causes
 569 .B mke2fs
 570 to not actually create a filesystem, but display what it
 571 would do if it were to create a filesystem.  This can be used to
 572 determine the location of the backup superblocks for a particular
 573 filesystem, so long as the
 574 .B mke2fs
 575 parameters that were passed when the
 576 filesystem was originally created are used again.  (With the
 577 .B \-n
 578 option added, of course!)
 579 .TP
 580 .BI \-N " number-of-inodes"
 581 Overrides the default calculation of the number of inodes that should be
 582 reserved for the filesystem (which is based on the number of blocks and
 583 the
 584 .I bytes-per-inode
 585 ratio).  This allows the user to specify the number
 586 of desired inodes directly.
 587 .TP
 588 .BI \-d " root-directory"
 589 Add the files from the root-directory to the filesystem.
 590 .TP
 591 .BI \-o " creator-os"
 592 Overrides the default value of the "creator operating system" field of the
 593 filesystem.  The creator field is set by default to the name of the OS the
 594 .B mke2fs
 595 executable was compiled for.
 596 .TP
 597 .B "\-O \fR[^]\fIfeature\fR[,...]"
 598 Create a filesystem with the given features (filesystem options),
 599 overriding the default filesystem options.  The features that are
 600 enabled by default are specified by the
 601 .I base_features
 602 relation, either in the
 603 .I [defaults]
 604 section in the
 605 .B /etc/mke2fs.conf
 606 configuration file,
 607 or in the
 608 .I [fs_types]
 609 subsections for the usage types as specified by the
 610 .B \-T
 611 option, further modified by the
 612 .I features
 613 relation found in the
 614 .I [fs_types]
 615 subsections for the filesystem and usage types.  See the
 616 .BR mke2fs.conf (5)
 617 manual page for more details.
 618 The filesystem type-specific configuration setting found in the
 619 .I [fs_types]
 620 section will override the global default found in
 621 .IR [defaults] .
 622 .sp
 623 The filesystem feature set will be further edited
 624 using either the feature set specified by this option,
 625 or if this option is not given, by the
 626 .I default_features
 627 relation for the filesystem type being created, or in the
 628 .I [defaults]
 629 section of the configuration file.
 630 .sp
 631 The filesystem feature set is comprised of a list of features, separated
 632 by commas, that are to be enabled.  To disable a feature, simply
 633 prefix the feature name with a caret ('^') character.
 634 Features with dependencies will not be removed successfully.
 635 The pseudo-filesystem feature "none" will clear all filesystem features.
 636 .TP
 637 For more information about the features which can be set, please see
 638 the manual page
 639 .BR ext4 (5).
 640 .TP
 641 .B \-q
 642 Quiet execution.  Useful if
 643 .B mke2fs
 644 is run in a script.
 645 .TP
 646 .BI \-r " revision"
 647 Set the filesystem revision for the new filesystem.  Note that 1.2
 648 kernels only support revision 0 filesystems.  The default is to
 649 create revision 1 filesystems.
 650 .TP
 651 .B \-S
 652 Write superblock and group descriptors only.  This is useful if all of
 653 the superblock and backup superblocks are corrupted, and a last-ditch
 654 recovery method is desired.  It causes
 655 .B mke2fs
 656 to reinitialize the
 657 superblock and group descriptors, while not touching the inode table
 658 and the block and inode bitmaps.  The
 659 .B e2fsck
 660 program should be run immediately after this option is used, and there
 661 is no guarantee that any data will be salvageable.  It is critical to
 662 specify the correct filesystem blocksize when using this option,
 663 or there is no chance of recovery.
 664 .\" .TP
 665 .\" .BI \-t " test"
 666 .\" Check the device for bad blocks before creating the file system
 667 .\" using the specified test.
 668 .TP
 669 .BI \-t " fs-type"
 670 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
 671 to be created.
 672 If this option is not specified,
 673 .B mke2fs
 674 will pick a default either via how
 675 the command was run (for example, using a name of the form mkfs.ext2,
 676 mkfs.ext3, etc.) or via a default as defined by the
 677 .B /etc/mke2fs.conf
 678 file.   This option controls which filesystem options are used by
 679 default, based on the
 680 .B fstypes
 681 configuration stanza in
 682 .BR /etc/mke2fs.conf .
 683 .sp
 684 If the
 685 .B \-O
 686 option is used to explicitly add or remove filesystem options that
 687 should be set in the newly created filesystem, the
 688 resulting filesystem may not be supported by the requested
 689 .IR fs-type .
 690 (e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
 691 filesystem that is not supported by the ext3 implementation as found in
 692 the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
 693 will create a filesystem that does not have a journal and hence will not
 694 be supported by the ext3 filesystem code in the Linux kernel.)
 695 .TP
 696 .BI \-T " usage-type[,...]"
 697 Specify how the filesystem is going to be used, so that
 698 .B mke2fs
 699 can choose optimal filesystem parameters for that use.  The usage
 700 types that are supported are defined in the configuration file
 701 .BR /etc/mke2fs.conf .
 702 The user may specify one or more usage types
 703 using a comma separated list.
 704 .sp
 705 If this option is is not specified,
 706 .B mke2fs
 707 will pick a single default usage type based on the size of the filesystem to
 708 be created.  If the filesystem size is less than 3 megabytes,
 709 .B mke2fs
 710 will use the filesystem type
 711 .IR floppy .
 712 If the filesystem size is greater than or equal to 3 but less than
 713 512 megabytes,
 714 .BR mke2fs (8)
 715 will use the filesystem type
 716 .IR small .
 717 If the filesystem size is greater than or equal to 4 terabytes but less than
 718 16 terabytes,
 719 .BR mke2fs (8)
 720 will use the filesystem type
 721 .IR big .
 722 If the filesystem size is greater than or equal to 16 terabytes,
 723 .BR mke2fs (8)
 724 will use the filesystem type
 725 .IR huge .
 726 Otherwise,
 727 .BR mke2fs (8)
 728 will use the default filesystem type
 729 .IR default .
 730 .TP
 731 .BI \-U " UUID"
 732 Create the filesystem with the specified UUID.
 733 .TP
 734 .B \-v
 735 Verbose execution.
 736 .TP
 737 .B \-V
 738 Print the version number of
 739 .B mke2fs
 740 and exit.
 741 .SH ENVIRONMENT
 742 .TP
 743 .BI MKE2FS_SYNC
 744 If set to non-zero integer value, its value is used to determine how often
 745 .BR sync (2)
 746 is called during inode table initialization.
 747 .TP
 748 .BI MKE2FS_CONFIG
 749 Determines the location of the configuration file (see
 750 .BR mke2fs.conf (5)).
 751 .TP
 752 .BI MKE2FS_FIRST_META_BG
 753 If set to non-zero integer value, its value is used to determine first meta
 754 block group. This is mostly for debugging purposes.
 755 .TP
 756 .BI MKE2FS_DEVICE_SECTSIZE
 757 If set to non-zero integer value, its value is used to determine physical
 758 sector size of the
 759 .IR device .
 760 .TP
 761 .BI MKE2FS_SKIP_CHECK_MSG
 762 If set, do not show the message of filesystem automatic check caused by
 763 mount count or check interval.
 764 .SH AUTHOR
 765 This version of
 766 .B mke2fs
 767 has been written by Theodore Ts'o <tytso@mit.edu>.
 768 .SH BUGS
 769 .B mke2fs
 770 accepts the
 771 .B \-f
 772 option but currently ignores it because the second
 773 extended file system does not support fragments yet.
 774 .br
 775 There may be other ones.  Please, report them to the author.
 776 .SH AVAILABILITY
 777 .B mke2fs
 778 is part of the e2fsprogs package and is available from
 779 http://e2fsprogs.sourceforge.net.
 780 .SH SEE ALSO
 781 .BR mke2fs.conf (5),
 782 .BR badblocks (8),
 783 .BR dumpe2fs (8),
 784 .BR e2fsck (8),
 785 .BR tune2fs (8),
 786 .BR ext4 (5)