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3839e657 1.\" -*- nroff -*-
a418d3ad
TT
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.
98794d0e 4.\"
74becf3c 5.TH MKE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
3839e657 6.SH NAME
4f858546 7mke2fs \- create an ext2/ext3/ext4 filesystem
3839e657
TT
8.SH SYNOPSIS
9.B mke2fs
10[
11.B \-c
98794d0e 12|
3839e657 13.B \-l
1e3472c5 14.I filename
3839e657
TT
15]
16[
17.B \-b
1e3472c5 18.I block-size
3839e657
TT
19]
20[
75dd3c47
TN
21.B \-C
22.I cluster-size
23]
24[
4407ea3b
DW
25.B \-d
26.I root-directory
27]
28[
37c8db7b
TT
29.B \-D
30]
31[
5e05541a
TT
32.B \-g
33.I blocks-per-group
34]
35[
9ba40002
TT
36.B \-G
37.I number-of-groups
38]
39[
3839e657 40.B \-i
1e3472c5 41.I bytes-per-inode
3839e657
TT
42]
43[
067911ae
AD
44.B \-I
45.I inode-size
46]
47[
85ef4ae8 48.B \-j
dc2ec525
TT
49]
50[
51.B \-J
8ddaa66b 52.I journal-options
85ef4ae8
TT
53]
54[
5515e6b4
TT
55.B \-N
56.I number-of-inodes
57]
58[
a26ba650 59.B \-n
2740156b
TT
60]
61[
3839e657 62.B \-m
1e3472c5
TT
63.I reserved-blocks-percentage
64]
65[
66.B \-o
67.I creator-os
3839e657
TT
68]
69[
98794d0e 70.B \-O
5c4c3876 71[^]\fIfeature\fR[,...]
896938d5
TT
72]
73[
f3db3566
TT
74.B \-q
75]
76[
caf8ce4c
TT
77.B \-r
78.I fs-revision-level
a29f4d30
TT
79]
80[
c6a44136
TT
81.B \-E
82.I extended-options
521e3685
TT
83]
84[
3839e657
TT
85.B \-v
86]
f3db3566 87[
74becf3c
TT
88.B \-F
89]
90[
1e3472c5
TT
91.B \-L
92.I volume-label
93]
94[
95.B \-M
96.I last-mounted-directory
97]
98[
f3db3566
TT
99.B \-S
100]
818180cd 101[
3d43836f
TT
102.B \-t
103.I fs-type
104]
105[
50787ea2 106.B \-T
3d43836f 107.I usage-type
50787ea2
TT
108]
109[
b0afdda1
TT
110.B \-U
111.I UUID
112]
113[
818180cd
TT
114.B \-V
115]
cd32129d
DW
116[
117.B \-e
118.I errors-behavior
119]
2d291b3c
DW
120[
121.B \-z
122.I undo_file
123]
1e3472c5 124.I device
3839e657 125[
9ac2930c 126.I fs-size
3839e657 127]
48015ced 128@JDEV@.sp
8d641749 129@JDEV@.B "mke2fs \-O journal_dev"
48015ced
TT
130@JDEV@[
131@JDEV@.B \-b
132@JDEV@.I block-size
133@JDEV@]
8d641749 134.\" No external-journal specific journal options yet (size is ignored)
48015ced
TT
135.\" @JDEV@[
136.\" @JDEV@.B \-J
137.\" @JDEV@.I journal-options
138.\" @JDEV@]
139@JDEV@[
140@JDEV@.B \-L
141@JDEV@.I volume-label
142@JDEV@]
143@JDEV@[
144@JDEV@.B \-n
145@JDEV@]
146@JDEV@[
147@JDEV@.B \-q
148@JDEV@]
149@JDEV@[
150@JDEV@.B \-v
151@JDEV@]
8d641749 152@JDEV@.I external-journal
2d15576d 153@JDEV@[
9ac2930c 154@JDEV@.I fs-size
2d15576d 155@JDEV@]
3839e657
TT
156.SH DESCRIPTION
157.B mke2fs
4f858546 158is used to create an ext2, ext3, or ext4 filesystem, usually in a disk
9ac2930c
TT
159partition (or file) named by
160.IR device .
161.PP
162The file system size is specified by
163.IR fs-size .
164If
165.I fs-size
166does not have a suffix, it is interpreted as power-of-two kilobytes,
167unless the
168.B \-b
169.I blocksize
170option is specified, in which case
171.I fs-size
172is interpreted as the number of
173.I blocksize
174blocks. If the fs-size is suffixed by 'k', 'm', 'g', 't'
175(either upper-case or lower-case), then it is interpreted in
176power-of-two kilobytes, megabytes, gigabytes, terabytes, etc.
177If
178.I fs-size
179is omitted,
3839e657 180.B mke2fs
9ac2930c
TT
181will create the file system based on the device size.
182.PP
183If
184.B mke2fs
185is run as
186.B mkfs.XXX
187(i.e.,
188.BR mkfs.ext2 ,
189.BR mkfs.ext3 ,
190or
191.BR mkfs.ext4 )
192the option
193.B \-t
194.I XXX
195is implied; so
0072f8de 196.B mkfs.ext3
9ac2930c
TT
197will create a file system for use with ext3,
198.B mkfs.ext4
199will create a file system for use with ext4, and so on.
de7a86e2
TT
200.PP
201The defaults of the parameters for the newly created filesystem, if not
202overridden by the options listed below, are controlled by the
203.B /etc/mke2fs.conf
204configuration file. See the
205.BR mke2fs.conf (5)
206manual page for more details.
3839e657
TT
207.SH OPTIONS
208.TP
caf8ce4c 209.BI \-b " block-size"
98794d0e 210Specify the size of blocks in bytes. Valid block-size values are 1024,
06968e7e 2112048 and 4096 bytes per block. If omitted,
98794d0e 212block-size is heuristically determined by the filesystem size and
c5290fae 213the expected usage of the filesystem (see the
06968e7e 214.B \-T
98794d0e 215option). If
c5290fae 216.I block-size
eddf36ba 217is preceded by a negative sign ('-'), then
c6a44136
TT
218.B mke2fs
219will use heuristics to determine the
c5290fae 220appropriate block size, with the constraint that the block size will be
98794d0e 221at least
c5290fae
TT
222.I block-size
223bytes. This is useful for certain hardware devices which require that
224the blocksize be a multiple of 2k.
3839e657 225.TP
caf8ce4c 226.B \-c
3ed57c27 227Check the device for bad blocks before creating the file system. If
98794d0e 228this option is specified twice, then a slower read-write
3ed57c27 229test is used instead of a fast read-only test.
3839e657 230.TP
0f680ee8
ZL
231.B \-C " cluster-size"
232Specify the size of cluster in bytes for filesystems using the bigalloc
233feature. Valid cluster-size values are from 2048 to 256M bytes per
9518b297
TT
234cluster. This can only be specified if the bigalloc feature is
235enabled. (See the
236.B ext4 (5)
237man page for more details about bigalloc.) The default cluster size if
238bigalloc is enabled is 16 times the block size.
0f680ee8 239.TP
4407ea3b
DW
240.BI \-d " root-directory"
241Copy the contents of the given directory into the root directory of the
242filesystem.
243.TP
37c8db7b
TT
244.B \-D
245Use direct I/O when writing to the disk. This avoids mke2fs dirtying a
246lot of buffer cache memory, which may impact other applications running
247on a busy server. This option will cause mke2fs to run much more
248slowly, however, so there is a tradeoff to using direct I/O.
249.TP
cd32129d
DW
250.BI \-e " error-behavior"
251Change the behavior of the kernel code when errors are detected.
252In all cases, a filesystem error will cause
253.BR e2fsck (8)
254to check the filesystem on the next boot.
255.I error-behavior
256can be one of the following:
257.RS 1.2i
258.TP 1.2i
259.B continue
260Continue normal execution.
261.TP
262.B remount-ro
263Remount filesystem read-only.
264.TP
265.B panic
266Cause a kernel panic.
267.RE
268.TP
c6a44136
TT
269.BI \-E " extended-options"
270Set extended options for the filesystem. Extended options are comma
271separated, and may take an argument using the equals ('=') sign. The
a26ba650 272.B \-E
98794d0e 273option used to be
a26ba650 274.B \-R
98794d0e 275in earlier versions of
c6a44136 276.BR mke2fs .
98794d0e 277The
a26ba650 278.B \-R
b769aaec
AD
279option is still accepted for backwards compatibility, but is deprecated.
280The following extended options are supported:
c6a44136
TT
281.RS 1.2i
282.TP
0f5eba75
AD
283.BI mmp_update_interval= interval
284Adjust the initial MMP update interval to
285.I interval
286seconds. Specifying an
287.I interval
288of 0 means to use the default interval. The specified interval must
289be less than 300 seconds. Requires that the
290.B mmp
291feature be enabled.
292.TP
0c17cb25 293.BI stride= stride-size
c6a44136 294Configure the filesystem for a RAID array with
0c17cb25
TT
295.I stride-size
296filesystem blocks. This is the number of blocks read or written to disk
98794d0e 297before moving to the next disk, which is sometimes referred to as the
2ac7f066
TT
298.I chunk size.
299This mostly affects placement of filesystem metadata like bitmaps at
a4396e9d 300.B mke2fs
98794d0e
BS
301time to avoid placing them on a single disk, which can hurt performance.
302It may also be used by the block allocator.
0c17cb25 303.TP
d4c0d8e5 304.BI stripe_width= stripe-width
0c17cb25
TT
305Configure the filesystem for a RAID array with
306.I stripe-width
98794d0e 307filesystem blocks per stripe. This is typically stride-size * N, where
2ac7f066 308N is the number of data-bearing disks in the RAID (e.g. for RAID 5 there is one
98794d0e 309parity disk, so N will be the number of disks in the array minus 1).
0c17cb25
TT
310This allows the block allocator to prevent read-modify-write of the
311parity in a RAID stripe if possible when the data is written.
c6a44136 312.TP
88ee023b
TT
313.BI offset= offset
314Create the filesystem at an offset from the beginning of the device or
315file. This can be useful when creating disk images for virtual machines.
316.TP
c6a44136
TT
317.BI resize= max-online-resize
318Reserve enough space so that the block group descriptor table can grow
98794d0e
BS
319to support a filesystem that has
320.I max-online-resize
321blocks.
6cb27404 322.TP
3b4a66cf 323.B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
a4396e9d 324If enabled and the uninit_bg feature is enabled, the inode table will
98794d0e 325not be fully initialized by
a4396e9d
TT
326.BR mke2fs .
327This speeds up filesystem
98794d0e 328initialization noticeably, but it requires the kernel to finish
a4396e9d 329initializing the filesystem in the background when the filesystem is
43781b94 330first mounted. If the option value is omitted, it defaults to 1 to
6c54689f
AD
331enable lazy inode table zeroing.
332.TP
333.B lazy_journal_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
334If enabled, the journal inode will not be fully zeroed out by
335.BR mke2fs .
336This speeds up filesystem initialization noticeably, but carries some
337small risk if the system crashes before the journal has been overwritten
338entirely one time. If the option value is omitted, it defaults to 1 to
339enable lazy journal inode zeroing.
a4396e9d 340.TP
65c6c3e0
TT
341.BI num_backup_sb= <0|1|2>
342If the
343.B sparse_super2
344file system feature is enabled this option controls whether there will
345be 0, 1, or 2 backup superblocks created in the file system.
346.TP
3c6e91c5
TT
347.B packed_meta_blocks\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
348Place the allocation bitmaps and the inode table at the beginning of the
349disk. This option requires that the flex_bg file system feature to be
350enabled in order for it to have effect, and will also create the journal
351at the beginning of the file system. This option is useful for flash
352devices that use SLC flash at the beginning of the disk.
353It also maximizes the range of contiguous data blocks, which
354can be useful for certain specialized use cases, such as supported
355Shingled Drives.
356.TP
dc9cc700
AD
357.BI root_owner [=uid:gid]
358Specify the numeric user and group ID of the root directory. If no UID:GID
359is specified, use the user and group ID of the user running \fBmke2fs\fR.
360In \fBmke2fs\fR 1.42 and earlier the UID and GID of the root directory were
361set by default to the UID and GID of the user running the mke2fs command.
362The \fBroot_owner=\fR option allows explicitly specifying these values,
363and avoid side-effects for users that do not expect the contents of the
364filesystem to change based on the user running \fBmke2fs\fR.
365.TP
6cb27404
TT
366.B test_fs
367Set a flag in the filesystem superblock indicating that it may be
368mounted using experimental kernel code, such as the ext4dev filesystem.
0bc85dfb
LC
369.TP
370.BI discard
371Attempt to discard blocks at mkfs time (discarding blocks initially is useful
372on solid state devices and sparse / thin-provisioned storage). When the device
373advertises that discard also zeroes data (any subsequent read after the discard
374and before write returns zero), then mark all not-yet-zeroed inode tables as
375zeroed. This significantly speeds up filesystem initialization. This is set
376as default.
377.TP
378.BI nodiscard
855a77a1 379Do not attempt to discard blocks at mkfs time.
9e8fcd6e
TT
380.TP
381.BI quotatype
bc8f1ae5
TT
382Specify the which quota types (usrquota, grpquota, prjquota) which
383should be enabled in the created file system. The argument of this
384extended option should be a colon separated list. This option has
385effect only if the
9e8fcd6e 386.B quota
bc8f1ae5
TT
387feature is set. The default quota types to be initialized if this
388option is not specified is both user and group quotas. If the project
389feature is enabled that project quotas will be initialized as well.
c6a44136
TT
390.RE
391.TP
48015ced 392.B \-F
98794d0e 393Force
48015ced 394.B mke2fs
c16e610c
AD
395to create a filesystem, even if the specified device is not a partition
396on a block special device, or if other parameters do not make sense.
98794d0e 397In order to force
c16e610c 398.B mke2fs
98794d0e 399to create a filesystem even if the filesystem appears to be in use
c16e610c
AD
400or is mounted (a truly dangerous thing to do), this option must be
401specified twice.
48015ced 402.TP
5e05541a
TT
403.BI \-g " blocks-per-group"
404Specify the number of blocks in a block group. There is generally no
98794d0e 405reason for the user to ever set this parameter, as the default is optimal
5e05541a
TT
406for the filesystem. (For administrators who are creating
407filesystems on RAID arrays, it is preferable to use the
408.I stride
409RAID parameter as part of the
e28a1bca 410.B \-E
98794d0e 411option rather than manipulating the number of blocks per group.)
5e05541a 412This option is generally used by developers who
98794d0e 413are developing test cases.
0f680ee8
ZL
414.IP
415If the bigalloc feature is enabled, the
416.B \-g
417option will specify the number of clusters in a block group.
5e05541a 418.TP
9ba40002 419.BI \-G " number-of-groups"
98794d0e 420Specify the number of block groups that will be packed together to
7a9f055f
TT
421create a larger virtual block group (or "flex_bg group") in an
422ext4 filesystem. This improves meta-data locality and performance
423on meta-data heavy workloads. The number of groups must be a power
d04ad325 424of 2 and may only be specified if the
7a9f055f
TT
425.B flex_bg
426filesystem feature is enabled.
9ba40002 427.TP
caf8ce4c 428.BI \-i " bytes-per-inode"
98794d0e 429Specify the bytes/inode ratio.
3839e657
TT
430.B mke2fs
431creates an inode for every
432.I bytes-per-inode
98794d0e 433bytes of space on the disk. The larger the
caf8ce4c 434.I bytes-per-inode
48015ced 435ratio, the fewer inodes will be created. This value generally shouldn't
98794d0e
BS
436be smaller than the blocksize of the filesystem, since in that case more
437inodes would be made than can ever be used. Be warned that it is not
e2883e27
PS
438possible to change this ratio on a filesystem after it is created, so be
439careful deciding the correct value for this parameter. Note that resizing
ce20096f 440a filesystem changes the number of inodes to maintain this ratio.
067911ae
AD
441.TP
442.BI \-I " inode-size"
98794d0e 443Specify the size of each inode in bytes.
886056bd 444The
067911ae 445.I inode-size
98794d0e 446value must be a power of 2 larger or equal to 128. The larger the
067911ae
AD
447.I inode-size
448the more space the inode table will consume, and this reduces the usable
98794d0e 449space in the filesystem and can also negatively impact performance.
886056bd
TT
450It is not
451possible to change this value after the filesystem is created.
452.IP
453In kernels after 2.6.10 and some
454earlier vendor kernels it is possible to utilize inodes larger than
455128 bytes to store
456extended attributes for improved performance.
e67670c3 457Extended attributes
067911ae 458stored in large inodes are not visible with older kernels, and such
d04ad325 459filesystems will not be mountable with 2.4 kernels at all.
886056bd
TT
460.IP
461The default inode size is controlled by the
462.BR mke2fs.conf (5)
463file. In the
464.B mke2fs.conf
465file shipped with e2fsprogs, the default inode size is 256 bytes for
466most file systems, except for small file systems where the inode size
467will be 128 bytes.
98794d0e 468.TP
48015ced
TT
469.B \-j
470Create the filesystem with an ext3 journal. If the
dc2ec525 471.B \-J
48015ced 472option is not specified, the default journal parameters will be used to
98794d0e 473create an appropriately sized journal (given the size of the filesystem)
48015ced
TT
474stored within the filesystem. Note that you must be using a kernel
475which has ext3 support in order to actually make use of the journal.
dc2ec525 476.TP
48015ced 477.BI \-J " journal-options"
dc2ec525 478Create the ext3 journal using options specified on the command-line.
8ddaa66b
TT
479Journal options are comma
480separated, and may take an argument using the equals ('=') sign.
48015ced
TT
481The following journal options are supported:
482.RS 1.2i
dc2ec525 483.TP
48015ced 484.BI size= journal-size
f0865ce4 485Create an internal journal (i.e., stored inside the filesystem) of size
98794d0e 486.I journal-size
8d641749 487megabytes.
98794d0e
BS
488The size of the journal must be at least 1024 filesystem blocks
489(i.e., 1MB if using 1k blocks, 4MB if using 4k blocks, etc.)
57cb2716
SP
490and may be no more than 10,240,000 filesystem blocks or half the total
491file system size (whichever is smaller)
b818205f
TT
492.TP
493.BI location =journal-location
494Specify the location of the journal. The argument
495.I journal-location
496can either be specified as a block number, or if the number has a units
497suffix (e.g., 'M', 'G', etc.) interpret it as the offset from the
498beginning of the file system.
48015ced
TT
499@JDEV@.TP
500@JDEV@.BI device= external-journal
8d641749
TT
501@JDEV@Attach the filesystem to the journal block device located on
502@JDEV@.IR external-journal .
503@JDEV@The external
504@JDEV@journal must already have been created using the command
505@JDEV@.IP
2d15576d
AD
506@JDEV@.B mke2fs -O journal_dev
507@JDEV@.I external-journal
8d641749
TT
508@JDEV@.IP
509@JDEV@Note that
510@JDEV@.I external-journal
511@JDEV@must have been created with the
512@JDEV@same block size as the new filesystem.
3024d887
TT
513@JDEV@In addition, while there is support for attaching
514@JDEV@multiple filesystems to a single external journal,
98794d0e 515@JDEV@the Linux kernel and
3024d887
TT
516@JDEV@.BR e2fsck (8)
517@JDEV@do not currently support shared external journals yet.
2d15576d
AD
518@JDEV@.IP
519@JDEV@Instead of specifying a device name directly,
520@JDEV@.I external-journal
521@JDEV@can also be specified by either
522@JDEV@.BI LABEL= label
523@JDEV@or
524@JDEV@.BI UUID= UUID
525@JDEV@to locate the external journal by either the volume label or UUID
526@JDEV@stored in the ext2 superblock at the start of the journal. Use
527@JDEV@.BR dumpe2fs (8)
528@JDEV@to display a journal device's volume label and UUID. See also the
529@JDEV@.B -L
530@JDEV@option of
531@JDEV@.BR tune2fs (8).
8d641749
TT
532.RE
533@JDEV@.IP
48015ced
TT
534@JDEV@Only one of the
535@JDEV@.BR size " or " device
536@JDEV@options can be given for a filesystem.
48015ced
TT
537.TP
538.BI \-l " filename"
539Read the bad blocks list from
98794d0e 540.IR filename .
3ed57c27 541Note that the block numbers in the bad block list must be generated
98794d0e
BS
542using the same block size as used by
543.BR mke2fs .
544As a result, the
3ed57c27 545.B \-c
98794d0e 546option to
3ed57c27
TT
547.B mke2fs
548is a much simpler and less error-prone method of checking a disk for bad
98794d0e 549blocks before formatting it, as
3ed57c27
TT
550.B mke2fs
551will automatically pass the correct parameters to the
552.B badblocks
553program.
48015ced 554.TP
6a7075df
TT
555.BI \-L " new-volume-label"
556Set the volume label for the filesystem to
557.IR new-volume-label .
558The maximum length of the
559volume label is 16 bytes.
48015ced
TT
560.TP
561.BI \-m " reserved-blocks-percentage"
98794d0e 562Specify the percentage of the filesystem blocks reserved for
029de632 563the super-user. This avoids fragmentation, and allows root-owned
98794d0e 564daemons, such as
029de632 565.BR syslogd (8),
98794d0e
BS
566to continue to function correctly after non-privileged processes are
567prevented from writing to the filesystem. The default percentage
029de632 568is 5%.
dc2ec525 569.TP
98794d0e
BS
570.BI \-M " last-mounted-directory"
571Set the last mounted directory for the filesystem. This might be useful
572for the sake of utilities that key off of the last mounted directory to
bcf5aea2 573determine where the filesystem should be mounted.
85ef4ae8 574.TP
caf8ce4c 575.B \-n
98794d0e
BS
576Causes
577.B mke2fs
578to not actually create a filesystem, but display what it
1f22ce34
TT
579would do if it were to create a filesystem. This can be used to
580determine the location of the backup superblocks for a particular
98794d0e
BS
581filesystem, so long as the
582.B mke2fs
583parameters that were passed when the
1f22ce34 584filesystem was originally created are used again. (With the
98794d0e 585.B \-n
1f22ce34 586option added, of course!)
2740156b 587.TP
caf8ce4c 588.BI \-N " number-of-inodes"
98794d0e
BS
589Overrides the default calculation of the number of inodes that should be
590reserved for the filesystem (which is based on the number of blocks and
591the
caf8ce4c 592.I bytes-per-inode
98794d0e 593ratio). This allows the user to specify the number
5515e6b4
TT
594of desired inodes directly.
595.TP
48015ced 596.BI \-o " creator-os"
98794d0e
BS
597Overrides the default value of the "creator operating system" field of the
598filesystem. The creator field is set by default to the name of the OS the
583ccdc3 599.B mke2fs
98794d0e 600executable was compiled for.
1e3472c5 601.TP
5c4c3876 602.B "\-O \fR[^]\fIfeature\fR[,...]"
98794d0e
BS
603Create a filesystem with the given features (filesystem options),
604overriding the default filesystem options. The features that are
9dc6ad1e
TT
605enabled by default are specified by the
606.I base_features
607relation, either in the
98794d0e 608.I [defaults]
9dc6ad1e
TT
609section in the
610.B /etc/mke2fs.conf
3d43836f 611configuration file,
98794d0e 612or in the
9dc6ad1e 613.I [fs_types]
98794d0e 614subsections for the usage types as specified by the
a26ba650 615.B \-T
3d43836f
TT
616option, further modified by the
617.I features
618relation found in the
98794d0e
BS
619.I [fs_types]
620subsections for the filesystem and usage types. See the
3d43836f
TT
621.BR mke2fs.conf (5)
622manual page for more details.
623The filesystem type-specific configuration setting found in the
9dc6ad1e
TT
624.I [fs_types]
625section will override the global default found in
98794d0e 626.IR [defaults] .
48015ced 627.sp
98794d0e
BS
628The filesystem feature set will be further edited
629using either the feature set specified by this option,
630or if this option is not given, by the
9dc6ad1e 631.I default_features
98794d0e
BS
632relation for the filesystem type being created, or in the
633.I [defaults]
9dc6ad1e
TT
634section of the configuration file.
635.sp
636The filesystem feature set is comprised of a list of features, separated
637by commas, that are to be enabled. To disable a feature, simply
5c4c3876 638prefix the feature name with a caret ('^') character.
3c22bf7e 639Features with dependencies will not be removed successfully.
4727c67d 640The pseudo-filesystem feature "none" will clear all filesystem features.
4727c67d 641.TP
3c22bf7e
TT
642For more information about the features which can be set, please see
643the manual page
644.BR ext4 (5).
1e3472c5 645.TP
8d641749 646.B \-q
98794d0e 647Quiet execution. Useful if
8d641749
TT
648.B mke2fs
649is run in a script.
650.TP
48015ced 651.BI \-r " revision"
a29f4d30 652Set the filesystem revision for the new filesystem. Note that 1.2
98794d0e 653kernels only support revision 0 filesystems. The default is to
48015ced 654create revision 1 filesystems.
a29f4d30 655.TP
caf8ce4c 656.B \-S
a6eeac1c
AD
657Write superblock and group descriptors only. This is an extreme
658measure to be taken only in the very unlikely case that all of
f3db3566 659the superblock and backup superblocks are corrupted, and a last-ditch
a6eeac1c 660recovery method is desired by experienced users. It causes
583ccdc3 661.B mke2fs
a6eeac1c
AD
662to reinitialize the superblock and group descriptors, while not
663touching the inode table and the block and inode bitmaps. The
f3db3566
TT
664.B e2fsck
665program should be run immediately after this option is used, and there
a6eeac1c
AD
666is no guarantee that any data will be salvageable. Due to the wide
667variety of possible options to
668.BR mke2fs
a7dc56f4 669that affect the on-disk layout, it is critical to specify exactly
a6eeac1c
AD
670the same format options, such as blocksize, fs-type, feature flags, and
671other tunables when using this option, or the filesystem will be further
672corrupted. In some cases, such as filesystems that have been resized,
673or have had features enabled after format time, it is impossible to
a7dc56f4 674overwrite all of the superblocks correctly, and at least some filesystem
a6eeac1c
AD
675corruption will occur. It is best to run this on a full copy of the
676filesystem so other options can be tried if this doesn't work.
8d641749
TT
677.\" .TP
678.\" .BI \-t " test"
679.\" Check the device for bad blocks before creating the file system
680.\" using the specified test.
818180cd 681.TP
3d43836f 682.BI \-t " fs-type"
4727c67d
UC
683Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is
684to be created.
98794d0e
BS
685If this option is not specified,
686.B mke2fs
687will pick a default either via how
688the command was run (for example, using a name of the form mkfs.ext2,
3d43836f 689mkfs.ext3, etc.) or via a default as defined by the
626a2e74 690.B /etc/mke2fs.conf
08c8b1ab
TT
691file. This option controls which filesystem options are used by
692default, based on the
693.B fstypes
694configuration stanza in
626a2e74 695.BR /etc/mke2fs.conf .
08c8b1ab
TT
696.sp
697If the
698.B \-O
699option is used to explicitly add or remove filesystem options that
700should be set in the newly created filesystem, the
701resulting filesystem may not be supported by the requested
702.IR fs-type .
b7150807 703(e.g., "\fBmke2fs \-t ext3 \-O extent /dev/sdXX\fR" will create a
08c8b1ab 704filesystem that is not supported by the ext3 implementation as found in
93aa0246 705the Linux kernel; and "\fBmke2fs \-t ext3 \-O ^has_journal /dev/hdXX\fR"
08c8b1ab
TT
706will create a filesystem that does not have a journal and hence will not
707be supported by the ext3 filesystem code in the Linux kernel.)
3d43836f
TT
708.TP
709.BI \-T " usage-type[,...]"
98794d0e
BS
710Specify how the filesystem is going to be used, so that
711.B mke2fs
3d43836f
TT
712can choose optimal filesystem parameters for that use. The usage
713types that are supported are defined in the configuration file
626a2e74 714.BR /etc/mke2fs.conf .
3d43836f
TT
715The user may specify one or more usage types
716using a comma separated list.
717.sp
718If this option is is not specified,
719.B mke2fs
720will pick a single default usage type based on the size of the filesystem to
0745e787 721be created. If the filesystem size is less than 3 megabytes,
a4396e9d 722.B mke2fs
3d43836f
TT
723will use the filesystem type
724.IR floppy .
0745e787 725If the filesystem size is greater than or equal to 3 but less than
3d43836f
TT
726512 megabytes,
727.BR mke2fs (8)
9a2767ff 728will use the filesystem type
3d43836f 729.IR small .
9a2767ff
NK
730If the filesystem size is greater than or equal to 4 terabytes but less than
73116 terabytes,
732.BR mke2fs (8)
733will use the filesystem type
734.IR big .
735If the filesystem size is greater than or equal to 16 terabytes,
736.BR mke2fs (8)
737will use the filesystem type
738.IR huge .
3d43836f
TT
739Otherwise,
740.BR mke2fs (8)
741will use the default filesystem type
742.IR default .
48015ced 743.TP
b0afdda1 744.BI \-U " UUID"
665ebf37
DD
745Set the universally unique identifier (UUID) of the filesystem to
746.IR UUID .
747The format of the UUID is a series of hex digits separated by hyphens,
748like this:
749"c1b9d5a2-f162-11cf-9ece-0020afc76f16".
750The
751.I UUID
752parameter may also be one of the following:
753.RS 1.2i
754.TP
755.I clear
756clear the filesystem UUID
757.TP
758.I random
759generate a new randomly-generated UUID
760.TP
761.I time
762generate a new time-based UUID
763.RE
b0afdda1 764.TP
48015ced
TT
765.B \-v
766Verbose execution.
50787ea2 767.TP
caf8ce4c 768.B \-V
98794d0e 769Print the version number of
818180cd
TT
770.B mke2fs
771and exit.
2d291b3c
DW
772.TP
773.BI \-z " undo_file"
774Before overwriting a file system block, write the old contents of the block to
775an undo file. This undo file can be used with e2undo(8) to restore the old
776contents of the file system should something go wrong. If the empty string is
777passed as the undo_file argument, the undo file will be written to a file named
778mke2fs-\fIdevice\fR.e2undo in the directory specified via the
779\fIE2FSPROGS_UNDO_DIR\fR environment variable or the \fIundo_dir\fR directive
780in the configuration file.
781
782WARNING: The undo file cannot be used to recover from a power or system crash.
5182ad4c
NK
783.SH ENVIRONMENT
784.TP
785.BI MKE2FS_SYNC
786If set to non-zero integer value, its value is used to determine how often
787.BR sync (2)
788is called during inode table initialization.
789.TP
790.BI MKE2FS_CONFIG
791Determines the location of the configuration file (see
792.BR mke2fs.conf (5)).
793.TP
794.BI MKE2FS_FIRST_META_BG
795If set to non-zero integer value, its value is used to determine first meta
796block group. This is mostly for debugging purposes.
797.TP
798.BI MKE2FS_DEVICE_SECTSIZE
75dd3c47
TN
799If set to non-zero integer value, its value is used to determine logical
800sector size of the
801.IR device .
802.TP
803.BI MKE2FS_DEVICE_PHYS_SECTSIZE
5182ad4c
NK
804If set to non-zero integer value, its value is used to determine physical
805sector size of the
806.IR device .
807.TP
808.BI MKE2FS_SKIP_CHECK_MSG
809If set, do not show the message of filesystem automatic check caused by
810mount count or check interval.
3839e657
TT
811.SH AUTHOR
812This version of
813.B mke2fs
a418d3ad 814has been written by Theodore Ts'o <tytso@mit.edu>.
3839e657
TT
815.SH AVAILABILITY
816.B mke2fs
98794d0e 817is part of the e2fsprogs package and is available from
348e43dc 818http://e2fsprogs.sourceforge.net.
3839e657 819.SH SEE ALSO
9dc6ad1e 820.BR mke2fs.conf (5),
e72a9ba3 821.BR badblocks (8),
3839e657
TT
822.BR dumpe2fs (8),
823.BR e2fsck (8),
3c22bf7e
TT
824.BR tune2fs (8),
825.BR ext4 (5)