1MKE2FS(8) System Manager's Manual MKE2FS(8)
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6 mke2fs - create an ext2/ext3/ext4 filesystem
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9 mke2fs [ -c | -l filename ] [ -b block-size ] [ -f fragment-size ] [ -g
10 blocks-per-group ] [ -G number-of-groups ] [ -i bytes-per-inode ] [ -I
11 inode-size ] [ -j ] [ -J journal-options ] [ -K ] [ -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 negative, then mke2fs will use heuristics to determine
41 the appropriate block size, with the constraint that the block
42 size will be at least block-size bytes. This is useful for cer‐
43 tain hardware devices which require that the blocksize be a mul‐
44 tiple 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 -E extended-options
51 Set extended options for the filesystem. Extended options are
52 comma separated, and may take an argument using the equals ('=')
53 sign. The -E option used to be -R in earlier versions of
54 mke2fs. The -R option is still accepted for backwards compati‐
55 bility. The following extended options are supported:
56 stride=stride-size
58 Configure the filesystem for a RAID array with
59 stride-size filesystem blocks. This is the number of
60 blocks read or written to disk before moving to the
61 next disk, which is sometimes referred to as the
62 chunk size. This mostly affects placement of
63 filesystem metadata like bitmaps at mke2fs time to
64 avoid placing them on a single disk, which can hurt
65 performance. It may also be used by the block allo‐
66 cator.
67 stripe-width=stripe-width
69 Configure the filesystem for a RAID array with
70 stripe-width filesystem blocks per stripe. This is
71 typically stride-size * N, where N is the number of
72 data-bearing disks in the RAID (e.g. for RAID 5
73 there is one parity disk, so N will be the number of
74 disks in the array minus 1). This allows the block
75 allocator to prevent read-modify-write of the parity
76 in a RAID stripe if possible when the data is writ‐
77 ten.
78 resize=max-online-resize
80 Reserve enough space so that the block group
81 descriptor table can grow to support a filesystem
82 that has max-online-resize blocks.
83 lazy_itable_init[= <0 to disable, 1 to enable>]
85 If enabled and the uninit_bg feature is enabled, the
86 inode table will not be fully initialized by mke2fs.
87 This speeds up filesystem initialization noticeably,
88 but it requires the kernel to finish initializing
89 the filesystem in the background when the filesystem
90 is first mounted. If the option value is omitted,
91 it defaults to 1 to enable lazy inode table initial‐
92 ization.
93 test_fs
95 Set a flag in the filesystem superblock indicating
96 that it may be mounted using experimental kernel
97 code, such as the ext4dev filesystem.
98 -f fragment-size
100 Specify the size of fragments in bytes.
101 -F Force mke2fs to create a filesystem, even if the specified
103 device is not a partition on a block special device, or if other
104 parameters do not make sense. In order to force mke2fs to cre‐
105 ate a filesystem even if the filesystem appears to be in use or
106 is mounted (a truly dangerous thing to do), this option must be
107 specified twice.
108 -g blocks-per-group
110 Specify the number of blocks in a block group. There is gener‐
111 ally no reason for the user to ever set this parameter, as the
112 default is optimal for the filesystem. (For administrators who
113 are creating filesystems on RAID arrays, it is preferable to use
114 the stride RAID parameter as part of the -E option rather than
115 manipulating the number of blocks per group.) This option is
116 generally used by developers who are developing test cases.
117 -G number-of-groups
119 Specify the number of block groups that will be packed together
120 to create a larger virtual block group (or "flex_bg group") in
121 an ext4 filesystem. This improves meta-data locality and per‐
122 formance on meta-data heavy workloads. The number of groups
123 must be a power of 2 and may only be specified if the flex_bg
124 filesystem feature is enabled.
125 -i bytes-per-inode
127 Specify the bytes/inode ratio. mke2fs creates an inode for
128 every bytes-per-inode bytes of space on the disk. The larger
129 the bytes-per-inode ratio, the fewer inodes will be created.
130 This value generally shouldn't be smaller than the blocksize of
131 the filesystem, since in that case more inodes would be made
132 than can ever be used. Be warned that it is not possible to
133 expand the number of inodes on a filesystem after it is created,
134 so be careful deciding the correct value for this parameter.
135 -I inode-size
137 Specify the size of each inode in bytes. mke2fs creates
138 256-byte inodes by default. In kernels after 2.6.10 and some
139 earlier vendor kernels it is possible to utilize inodes larger
140 than 128 bytes to store extended attributes for improved perfor‐
141 mance. The inode-size value must be a power of 2 larger or
142 equal to 128. The larger the inode-size the more space the
143 inode table will consume, and this reduces the usable space in
144 the filesystem and can also negatively impact performance.
145 Extended attributes stored in large inodes are not visible with
146 older kernels, and such filesystems will not be mountable with
147 2.4 kernels at all. It is not possible to change this value
148 after the filesystem is created.
149 -j Create the filesystem with an ext3 journal. If the -J option is
151 not specified, the default journal parameters will be used to
152 create an appropriately sized journal (given the size of the
153 filesystem) stored within the filesystem. Note that you must be
154 using a kernel which has ext3 support in order to actually make
155 use of the journal.
156 -J journal-options
158 Create the ext3 journal using options specified on the command-
159 line. Journal options are comma separated, and may take an
160 argument using the equals ('=') sign. The following journal
161 options are supported:
162 size=journal-size
164 Create an internal journal (i.e., stored inside the
165 filesystem) of size journal-size megabytes. The
166 size of the journal must be at least 1024 filesystem
167 blocks (i.e., 1MB if using 1k blocks, 4MB if using
168 4k blocks, etc.) and may be no more than 102,400
169 filesystem blocks.
170 device=external-journal
172 Attach the filesystem to the journal block device
173 located on external-journal. The external journal
174 must already have been created using the command
175 mke2fs -O journal_dev external-journal
177 Note that external-journal must have been created
179 with the same block size as the new filesystem. In
180 addition, while there is support for attaching mul‐
181 tiple filesystems to a single external journal, the
182 Linux kernel and e2fsck(8) do not currently support
183 shared external journals yet.
184 Instead of specifying a device name directly, exter‐
186 nal-journal can also be specified by either
187 LABEL=label or UUID=UUID to locate the external
188 journal by either the volume label or UUID stored in
189 the ext2 superblock at the start of the journal.
190 Use dumpe2fs(8) to display a journal device's volume
191 label and UUID. See also the -L option of
192 tune2fs(8).
193 Only one of the size or device options can be given for a
195 filesystem.
196 -K Keep, do not attempt to discard blocks at mkfs time (discarding
198 blocks initially is useful on solid state devices and sparse /
199 thin-provisioned storage).
200 -l filename
202 Read the bad blocks list from filename. Note that the block
203 numbers in the bad block list must be generated using the same
204 block size as used by mke2fs. As a result, the -c option to
205 mke2fs is a much simpler and less error-prone method of checking
206 a disk for bad blocks before formatting it, as mke2fs will auto‐
207 matically pass the correct parameters to the badblocks program.
208 -L new-volume-label
210 Set the volume label for the filesystem to new-volume-label.
211 The maximum length of the volume label is 16 bytes.
212 -m reserved-blocks-percentage
214 Specify the percentage of the filesystem blocks reserved for the
215 super-user. This avoids fragmentation, and allows root-owned
216 daemons, such as syslogd(8), to continue to function correctly
217 after non-privileged processes are prevented from writing to the
218 filesystem. The default percentage is 5%.
219 -M last-mounted-directory
221 Set the last mounted directory for the filesystem. This might
222 be useful for the sake of utilities that key off of the last
223 mounted directory to determine where the filesystem should be
224 mounted.
225 -n Causes mke2fs to not actually create a filesystem, but display
227 what it would do if it were to create a filesystem. This can be
228 used to determine the location of the backup superblocks for a
229 particular filesystem, so long as the mke2fs parameters that
230 were passed when the filesystem was originally created are used
231 again. (With the -n option added, of course!)
232 -N number-of-inodes
234 Overrides the default calculation of the number of inodes that
235 should be reserved for the filesystem (which is based on the
236 number of blocks and the bytes-per-inode ratio). This allows
237 the user to specify the number of desired inodes directly.
238 -o creator-os
240 Overrides the default value of the "creator operating system"
241 field of the filesystem. The creator field is set by default to
242 the name of the OS the mke2fs executable was compiled for.
243 -O feature[,...]
245 Create a filesystem with the given features (filesystem
246 options), overriding the default filesystem options. The fea‐
247 tures that are enabled by default are specified by the base_fea‐
248 tures relation, either in the [defaults] section in the
249 /etc/mke2fs.conf configuration file, or in the [fs_types] sub‐
250 sections for the usage types as specified by the -T option, fur‐
251 ther modified by the features relation found in the [fs_types]
252 subsections for the filesystem and usage types. See the
253 mke2fs.conf(5) manual page for more details. The filesystem
254 type-specific configuration setting found in the [fs_types] sec‐
255 tion will override the global default found in [defaults].
256 The filesystem feature set will be further edited using either
258 the feature set specified by this option, or if this option is
259 not given, by the default_features relation for the filesystem
260 type being created, or in the [defaults] section of the configu‐
261 ration file.
262 The filesystem feature set is comprised of a list of features,
264 separated by commas, that are to be enabled. To disable a fea‐
265 ture, simply prefix the feature name with a caret ('^') charac‐
266 ter. The pseudo-filesystem feature "none" will clear all
267 filesystem features.
268 dir_index
270 Use hashed b-trees to speed up lookups in large
271 directories.
272 extent Instead of using the indirect block scheme for stor‐
274 ing the location of data blocks in an inode, use
275 extents instead. This is a much more efficient
276 encoding which speeds up filesystem access, espe‐
277 cially for large files.
278 filetype
280 Store file type information in directory entries.
281 flex_bg
283 Allow the per-block group metadata (allocation bit‐
284 maps and inode tables) to be placed anywhere on the
285 storage media. In addition, mke2fs will place the
286 per-block group metadata together starting at the
287 first block group of each "flex_bg group". The
288 size of the flex_bg group can be specified using the
289 -G option.
290 has_journal
292 Create an ext3 journal (as if using the -j option).
293 journal_dev
295 Create an external ext3 journal on the given device
296 instead of a regular ext2 filesystem. Note that
297 external-journal must be created with the same block
298 size as the filesystems that will be using it.
299 large_file
301 Filesystem can contain files that are greater than
302 2GB. (Modern kernels set this feature automatically
303 when a file > 2GB is created.)
304 resize_inode
306 Reserve space so the block group descriptor table
307 may grow in the future. Useful for online resizing
308 using resize2fs. By default mke2fs will attempt to
309 reserve enough space so that the filesystem may grow
310 to 1024 times its initial size. This can be changed
311 using the resize extended option.
312 sparse_super
314 Create a filesystem with fewer superblock backup
315 copies (saves space on large filesystems).
316 uninit_bg
318 Create a filesystem without initializing all of the
319 block groups. This feature also enables checksums
320 and highest-inode-used statistics in each block‐
321 group. This feature can speed up filesystem cre‐
322 ation time noticeably (if lazy_itable_init is
323 enabled), and can also reduce e2fsck time dramati‐
324 cally. It is only supported by the ext4 filesystem
325 in recent Linux kernels.
326 -q Quiet execution. Useful if mke2fs is run in a script.
328 -r revision
330 Set the filesystem revision for the new filesystem. Note that
331 1.2 kernels only support revision 0 filesystems. The default is
332 to create revision 1 filesystems.
333 -S Write superblock and group descriptors only. This is useful if
335 all of the superblock and backup superblocks are corrupted, and
336 a last-ditch recovery method is desired. It causes mke2fs to
337 reinitialize the superblock and group descriptors, while not
338 touching the inode table and the block and inode bitmaps. The
339 e2fsck program should be run immediately after this option is
340 used, and there is no guarantee that any data will be salvage‐
341 able. It is critical to specify the correct filesystem block‐
342 size when using this option, or there is no chance of recovery.
343 -t fs-type
345 Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that
346 is to be created. If this option is not specified, mke2fs will
347 pick a default either via how the command was run (for example,
348 using a name of the form mkfs.ext2, mkfs.ext3, etc.) or via a
349 default as defined by the /etc/mke2fs.conf(5) file. This
350 option controls which filesystem options are used by default,
351 based on the fstypes configuration stanza in
352 /etc/mke2fs.conf(5).
353 If the -O option is used to explicitly add or remove filesystem
355 options that should be set in the newly created filesystem, the
356 resulting filesystem may not be supported by the requested fs-
357 type. (e.g., "mke2fs -t ext3 -O extents /dev/sdXX" will create
358 a filesystem that is not supported by the ext3 implementation as
359 found in the Linux kernel; and "mke2fs -t ext3 -O ^has_journal
360 /dev/hdXX" will create a filesystem that does not have a journal
361 and hence will not be supported by the ext3 filesystem code in
362 the Linux kernel.)
363 -T usage-type[,...]
365 Specify how the filesystem is going to be used, so that mke2fs
366 can choose optimal filesystem parameters for that use. The
367 usage types that are supported are defined in the configuration
368 file /etc/mke2fs.conf(5). The user may specify one or more
369 usage types using a comma separated list.
370 If this option is is not specified, mke2fs will pick a single
372 default usage type based on the size of the filesystem to be
373 created. If the filesystem size is less than or equal to 3
374 megabytes, mke2fs will use the filesystem type floppy. If the
375 filesystem size is greater than 3 but less than or equal to 512
376 megabytes, mke2fs(8) will use the filesystem small. Otherwise,
377 mke2fs(8) will use the default filesystem type default.
378 -U UUID
380 Create the filesystem with the specified UUID.
381 -v Verbose execution.
383 -V Print the version number of mke2fs and exit.
385
387 This version of mke2fs has been written by Theodore Ts'o
388 <tytso@mit.edu>.
389
391 mke2fs accepts the -f option but currently ignores it because the sec‐
392 ond extended file system does not support fragments yet.
393 There may be other ones. Please, report them to the author.
394
396 mke2fs is part of the e2fsprogs package and is available from
397 http://e2fsprogs.sourceforge.net.
398
400 mke2fs.conf(5), badblocks(8), dumpe2fs(8), e2fsck(8), tune2fs(8)
401E2fsprogs version 1.41.12 May 2010 MKE2FS(8)