1MKE2FS(8) System Manager's Manual MKE2FS(8)
2
6 mke2fs - create an ext2/ext3/ext4 filesystem
7
9 mke2fs [ -c | -l filename ] [ -b block-size ] [ -D ] [ -f fragment-size
10 ] [ -g blocks-per-group ] [ -G number-of-groups ] [ -i bytes-per-inode
11 ] [ -I inode-size ] [ -j ] [ -J journal-options ] [ -N number-of-inodes
12 ] [ -n ] [ -m reserved-blocks-percentage ] [ -o creator-os ] [ -O fea‐
13 ture[,...] ] [ -q ] [ -r fs-revision-level ] [ -E extended-options ] [
14 -v ] [ -F ] [ -L volume-label ] [ -M last-mounted-directory ] [ -S ] [
15 -t fs-type ] [ -T usage-type ] [ -U UUID ] [ -V ] device [ blocks-count
16 ]
17 mke2fs -O journal_dev [ -b block-size ] [ -L volume-label ] [ -n ] [ -q
19 ] [ -v ] external-journal [ blocks-count ]
20
22 mke2fs is used to create an ext2, ext3, or ext4 filesystem, usually in
23 a disk partition. device is the special file corresponding to the
24 device (e.g /dev/hdXX). blocks-count is the number of blocks on the
25 device. If omitted, mke2fs automagically figures the file system size.
26 If called as mkfs.ext3 a journal is created as if the -j option was
27 specified.
28 The defaults of the parameters for the newly created filesystem, if not
30 overridden by the options listed below, are controlled by the
31 /etc/mke2fs.conf configuration file. See the mke2fs.conf(5) manual
32 page for more details.
33
35 -b block-size
36 Specify the size of blocks in bytes. Valid block-size values
37 are 1024, 2048 and 4096 bytes per block. If omitted, block-size
38 is heuristically determined by the filesystem size and the
39 expected usage of the filesystem (see the -T option). If block-
40 size is preceded by a negative sign ('-'), then mke2fs will use
41 heuristics to determine the appropriate block size, with the
42 constraint that the block size will be at least block-size
43 bytes. This is useful for certain hardware devices which
44 require that the blocksize be a multiple of 2k.
45 -c Check the device for bad blocks before creating the file system.
47 If this option is specified twice, then a slower read-write test
48 is used instead of a fast read-only test.
49 -C cluster-size
51 Specify the size of cluster in bytes for filesystems using the
52 bigalloc feature. Valid cluster-size values are from 2048 to
53 256M bytes per cluster. This can only be specified if the
54 bigalloc feature is enabled. (See the ext4 (5) man page for
55 more details about bigalloc.) The default cluster size if
56 bigalloc is enabled is 16 times the block size.
57 -D Use direct I/O when writing to the disk. This avoids mke2fs
59 dirtying a lot of buffer cache memory, which may impact other
60 applications running on a busy server. This option will cause
61 mke2fs to run much more slowly, however, so there is a tradeoff
62 to using direct I/O.
63 -E extended-options
65 Set extended options for the filesystem. Extended options are
66 comma separated, and may take an argument using the equals ('=')
67 sign. The -E option used to be -R in earlier versions of
68 mke2fs. The -R option is still accepted for backwards compati‐
69 bility, but is deprecated. The following extended options are
70 supported:
71 mmp_update_interval=interval
73 Adjust the initial MMP update interval to interval
74 seconds. Specifying an interval of 0 means to use
75 the default interval. The specified interval must
76 be less than 300 seconds. Requires that the mmp
77 feature be enabled.
78 stride=stride-size
80 Configure the filesystem for a RAID array with
81 stride-size filesystem blocks. This is the number of
82 blocks read or written to disk before moving to the
83 next disk, which is sometimes referred to as the
84 chunk size. This mostly affects placement of
85 filesystem metadata like bitmaps at mke2fs time to
86 avoid placing them on a single disk, which can hurt
87 performance. It may also be used by the block allo‐
88 cator.
89 stripe_width=stripe-width
91 Configure the filesystem for a RAID array with
92 stripe-width filesystem blocks per stripe. This is
93 typically stride-size * N, where N is the number of
94 data-bearing disks in the RAID (e.g. for RAID 5
95 there is one parity disk, so N will be the number of
96 disks in the array minus 1). This allows the block
97 allocator to prevent read-modify-write of the parity
98 in a RAID stripe if possible when the data is writ‐
99 ten.
100 resize=max-online-resize
102 Reserve enough space so that the block group
103 descriptor table can grow to support a filesystem
104 that has max-online-resize blocks.
105 lazy_itable_init[= <0 to disable, 1 to enable>]
107 If enabled and the uninit_bg feature is enabled, the
108 inode table will not be fully initialized by mke2fs.
109 This speeds up filesystem initialization noticeably,
110 but it requires the kernel to finish initializing
111 the filesystem in the background when the filesystem
112 is first mounted. If the option value is omitted,
113 it defaults to 1 to enable lazy inode table zeroing.
114 lazy_journal_init[= <0 to disable, 1 to enable>]
116 If enabled, the journal inode will not be fully
117 zeroed out by mke2fs. This speeds up filesystem
118 initialization noticeably, but carries some small
119 risk if the system crashes before the journal has
120 been overwritten entirely one time. If the option
121 value is omitted, it defaults to 1 to enable lazy
122 journal inode zeroing.
123 root_owner[=uid:gid]
125 Specify the numeric user and group ID of the root
126 directory. If no UID:GID is specified, use the user
127 and group ID of the user running mke2fs. In mke2fs
128 1.42 and earlier the UID and GID of the root direc‐
129 tory were set by default to the UID and GID of the
130 user running the mke2fs command. The root_owner=
131 option allows explicitly specifying these values,
132 and avoid side-effects for users that do not expect
133 the contents of the filesystem to change based on
134 the user running mke2fs.
135 test_fs
137 Set a flag in the filesystem superblock indicating
138 that it may be mounted using experimental kernel
139 code, such as the ext4dev filesystem.
140 discard
142 Attempt to discard blocks at mkfs time (discarding
143 blocks initially is useful on solid state devices
144 and sparse / thin-provisioned storage). When the
145 device advertises that discard also zeroes data (any
146 subsequent read after the discard and before write
147 returns zero), then mark all not-yet-zeroed inode
148 tables as zeroed. This significantly speeds up
149 filesystem initialization. This is set as default.
150 nodiscard
152 Do not attempt to discard blocks at mkfs time.
153 -f fragment-size
155 Specify the size of fragments in bytes.
156 -F Force mke2fs to create a filesystem, even if the specified
158 device is not a partition on a block special device, or if other
159 parameters do not make sense. In order to force mke2fs to cre‐
160 ate a filesystem even if the filesystem appears to be in use or
161 is mounted (a truly dangerous thing to do), this option must be
162 specified twice.
163 -g blocks-per-group
165 Specify the number of blocks in a block group. There is gener‐
166 ally no reason for the user to ever set this parameter, as the
167 default is optimal for the filesystem. (For administrators who
168 are creating filesystems on RAID arrays, it is preferable to use
169 the stride RAID parameter as part of the -E option rather than
170 manipulating the number of blocks per group.) This option is
171 generally used by developers who are developing test cases.
172 If the bigalloc feature is enabled, the -g option will specify
174 the number of clusters in a block group.
175 -G number-of-groups
177 Specify the number of block groups that will be packed together
178 to create a larger virtual block group (or "flex_bg group") in
179 an ext4 filesystem. This improves meta-data locality and per‐
180 formance on meta-data heavy workloads. The number of groups
181 must be a power of 2 and may only be specified if the flex_bg
182 filesystem feature is enabled.
183 -i bytes-per-inode
185 Specify the bytes/inode ratio. mke2fs creates an inode for
186 every bytes-per-inode bytes of space on the disk. The larger
187 the bytes-per-inode ratio, the fewer inodes will be created.
188 This value generally shouldn't be smaller than the blocksize of
189 the filesystem, since in that case more inodes would be made
190 than can ever be used. Be warned that it is not possible to
191 change this ratio on a filesystem after it is created, so be
192 careful deciding the correct value for this parameter. Note
193 that resizing a filesystem changes the numer of inodes to main‐
194 tain this ratio.
195 -I inode-size
197 Specify the size of each inode in bytes. The inode-size value
198 must be a power of 2 larger or equal to 128. The larger the
199 inode-size the more space the inode table will consume, and this
200 reduces the usable space in the filesystem and can also nega‐
201 tively impact performance. It is not possible to change this
202 value after the filesystem is created.
203 In kernels after 2.6.10 and some earlier vendor kernels it is
205 possible to utilize inodes larger than 128 bytes to store
206 extended attributes for improved performance. Extended
207 attributes stored in large inodes are not visible with older
208 kernels, and such filesystems will not be mountable with 2.4
209 kernels at all.
210 The default inode size is controlled by the mke2fs.conf(5) file.
212 In the mke2fs.conf file shipped with e2fsprogs, the default
213 inode size is 256 bytes for most file systems, except for small
214 file systems where the inode size will be 128 bytes.
215 -j Create the filesystem with an ext3 journal. If the -J option is
217 not specified, the default journal parameters will be used to
218 create an appropriately sized journal (given the size of the
219 filesystem) stored within the filesystem. Note that you must be
220 using a kernel which has ext3 support in order to actually make
221 use of the journal.
222 -J journal-options
224 Create the ext3 journal using options specified on the command-
225 line. Journal options are comma separated, and may take an
226 argument using the equals ('=') sign. The following journal
227 options are supported:
228 size=journal-size
230 Create an internal journal (i.e., stored inside the
231 filesystem) of size journal-size megabytes. The
232 size of the journal must be at least 1024 filesystem
233 blocks (i.e., 1MB if using 1k blocks, 4MB if using
234 4k blocks, etc.) and may be no more than 10,240,000
235 filesystem blocks or half the total file system size
236 (whichever is smaller)
237 device=external-journal
239 Attach the filesystem to the journal block device
240 located on external-journal. The external journal
241 must already have been created using the command
242 mke2fs -O journal_dev external-journal
244 Note that external-journal must have been created
246 with the same block size as the new filesystem. In
247 addition, while there is support for attaching mul‐
248 tiple filesystems to a single external journal, the
249 Linux kernel and e2fsck(8) do not currently support
250 shared external journals yet.
251 Instead of specifying a device name directly, exter‐
253 nal-journal can also be specified by either
254 LABEL=label or UUID=UUID to locate the external
255 journal by either the volume label or UUID stored in
256 the ext2 superblock at the start of the journal.
257 Use dumpe2fs(8) to display a journal device's volume
258 label and UUID. See also the -L option of
259 tune2fs(8).
260 Only one of the size or device options can be given for a
262 filesystem.
263 -l filename
265 Read the bad blocks list from filename. Note that the block
266 numbers in the bad block list must be generated using the same
267 block size as used by mke2fs. As a result, the -c option to
268 mke2fs is a much simpler and less error-prone method of checking
269 a disk for bad blocks before formatting it, as mke2fs will auto‐
270 matically pass the correct parameters to the badblocks program.
271 -L new-volume-label
273 Set the volume label for the filesystem to new-volume-label.
274 The maximum length of the volume label is 16 bytes.
275 -m reserved-blocks-percentage
277 Specify the percentage of the filesystem blocks reserved for the
278 super-user. This avoids fragmentation, and allows root-owned
279 daemons, such as syslogd(8), to continue to function correctly
280 after non-privileged processes are prevented from writing to the
281 filesystem. The default percentage is 5%.
282 -M last-mounted-directory
284 Set the last mounted directory for the filesystem. This might
285 be useful for the sake of utilities that key off of the last
286 mounted directory to determine where the filesystem should be
287 mounted.
288 -n Causes mke2fs to not actually create a filesystem, but display
290 what it would do if it were to create a filesystem. This can be
291 used to determine the location of the backup superblocks for a
292 particular filesystem, so long as the mke2fs parameters that
293 were passed when the filesystem was originally created are used
294 again. (With the -n option added, of course!)
295 -N number-of-inodes
297 Overrides the default calculation of the number of inodes that
298 should be reserved for the filesystem (which is based on the
299 number of blocks and the bytes-per-inode ratio). This allows
300 the user to specify the number of desired inodes directly.
301 -o creator-os
303 Overrides the default value of the "creator operating system"
304 field of the filesystem. The creator field is set by default to
305 the name of the OS the mke2fs executable was compiled for.
306 -O feature[,...]
308 Create a filesystem with the given features (filesystem
309 options), overriding the default filesystem options. The fea‐
310 tures that are enabled by default are specified by the base_fea‐
311 tures relation, either in the [defaults] section in the
312 /etc/mke2fs.conf configuration file, or in the [fs_types] sub‐
313 sections for the usage types as specified by the -T option, fur‐
314 ther modified by the features relation found in the [fs_types]
315 subsections for the filesystem and usage types. See the
316 mke2fs.conf(5) manual page for more details. The filesystem
317 type-specific configuration setting found in the [fs_types] sec‐
318 tion will override the global default found in [defaults].
319 The filesystem feature set will be further edited using either
321 the feature set specified by this option, or if this option is
322 not given, by the default_features relation for the filesystem
323 type being created, or in the [defaults] section of the configu‐
324 ration file.
325 The filesystem feature set is comprised of a list of features,
327 separated by commas, that are to be enabled. To disable a fea‐
328 ture, simply prefix the feature name with a caret ('^') or a
329 minus ('-') character. Features with dependencies will not be
330 removed successfully. The pseudo-filesystem feature "none" will
331 clear all filesystem features.
332 For more information about the features which can be set, please see
334 the manual page ext4(5).
335 -q Quiet execution. Useful if mke2fs is run in a script.
337 -r revision
339 Set the filesystem revision for the new filesystem. Note that
340 1.2 kernels only support revision 0 filesystems. The default is
341 to create revision 1 filesystems.
342 -S Write superblock and group descriptors only. This is useful if
344 all of the superblock and backup superblocks are corrupted, and
345 a last-ditch recovery method is desired. It causes mke2fs to
346 reinitialize the superblock and group descriptors, while not
347 touching the inode table and the block and inode bitmaps. The
348 e2fsck program should be run immediately after this option is
349 used, and there is no guarantee that any data will be salvage‐
350 able. It is critical to specify the correct filesystem block‐
351 size when using this option, or there is no chance of recovery.
352 -t fs-type
354 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that
355 is to be created. If this option is not specified, mke2fs will
356 pick a default either via how the command was run (for example,
357 using a name of the form mkfs.ext2, mkfs.ext3, etc.) or via a
358 default as defined by the /etc/mke2fs.conf file. This option
359 controls which filesystem options are used by default, based on
360 the fstypes configuration stanza in /etc/mke2fs.conf.
361 If the -O option is used to explicitly add or remove filesystem
363 options that should be set in the newly created filesystem, the
364 resulting filesystem may not be supported by the requested fs-
365 type. (e.g., "mke2fs -t ext3 -O extent /dev/sdXX" will create a
366 filesystem that is not supported by the ext3 implementation as
367 found in the Linux kernel; and "mke2fs -t ext3 -O ^has_journal
368 /dev/hdXX" will create a filesystem that does not have a journal
369 and hence will not be supported by the ext3 filesystem code in
370 the Linux kernel.)
371 -T usage-type[,...]
373 Specify how the filesystem is going to be used, so that mke2fs
374 can choose optimal filesystem parameters for that use. The
375 usage types that are supported are defined in the configuration
376 file /etc/mke2fs.conf. The user may specify one or more usage
377 types using a comma separated list.
378 If this option is is not specified, mke2fs will pick a single
380 default usage type based on the size of the filesystem to be
381 created. If the filesystem size is less than or equal to 3
382 megabytes, mke2fs will use the filesystem type floppy. If the
383 filesystem size is greater than 3 but less than or equal to 512
384 megabytes, mke2fs(8) will use the filesystem type small. If the
385 filesystem size is greater than or equal to 4 terabytes but less
386 than 16 terabytes, mke2fs(8) will use the filesystem type big.
387 If the filesystem size is greater than or equal to 16 terabytes,
388 mke2fs(8) will use the filesystem type huge. Otherwise,
389 mke2fs(8) will use the default filesystem type default.
390 -U UUID
392 Create the filesystem with the specified UUID.
393 -v Verbose execution.
395 -V Print the version number of mke2fs and exit.
397
399 MKE2FS_SYNC
400 If set to non-zero integer value, its value is used to determine
401 how often sync(2) is called during inode table initialization.
402 MKE2FS_CONFIG
404 Determines the location of the configuration file (see
405 mke2fs.conf(5)).
406 MKE2FS_FIRST_META_BG
408 If set to non-zero integer value, its value is used to determine
409 first meta block group. This is mostly for debugging purposes.
410 MKE2FS_DEVICE_SECTSIZE
412 If set to non-zero integer value, its value is used to determine
413 physical sector size of the device.
414 MKE2FS_SKIP_CHECK_MSG
416 If set, do not show the message of filesystem automatic check
417 caused by mount count or check interval.
418
420 This version of mke2fs has been written by Theodore Ts'o
421 <tytso@mit.edu>.
422
424 mke2fs accepts the -f option but currently ignores it because the sec‐
425 ond extended file system does not support fragments yet.
426 There may be other ones. Please, report them to the author.
427
429 mke2fs is part of the e2fsprogs package and is available from
430 http://e2fsprogs.sourceforge.net.
431
433 mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8),
434 ext4(5)
435E2fsprogs version 1.42.9 December 2013 MKE2FS(8)