1mke2fs.conf(5) File Formats Manual mke2fs.conf(5)
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6 mke2fs.conf - Configuration file for mke2fs
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9 mke2fs.conf is the configuration file for mke2fs(8). It controls the
10 default parameters used by mke2fs(8) when it is creating ext2, ext3, or
11 ext4 filesystems.
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13 The mke2fs.conf file uses an INI-style format. Stanzas, or top-level
14 sections, are delimited by square braces: [ ]. Within each section,
15 each line defines a relation, which assigns tags to values, or to a
16 subsection, which contains further relations or subsections. An exam‐
17 ple of the INI-style format used by this configuration file follows
18 below:
19
20 [section1]
21 tag1 = value_a
22 tag1 = value_b
23 tag2 = value_c
24
25 [section 2]
26 tag3 = {
27 subtag1 = subtag_value_a
28 subtag1 = subtag_value_b
29 subtag2 = subtag_value_c
30 }
31 tag1 = value_d
32 tag2 = value_e
33 }
34
35 Comments are delimited by a semicolon (';') or a hash ('#') character
36 at the beginning of the comment, and are terminated by the end of line
37 character.
38
39 Tags and values must be quoted using double quotes if they contain spa‐
40 ces. Within a quoted string, the standard backslash interpretations
41 apply: "\n" (for the newline character), "\t" (for the tab character),
42 "\b" (for the backspace character), and "\\" (for the backslash charac‐
43 ter).
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45 Some relations expect a boolean value. The parser is quite liberal on
46 recognizing ``yes'', '`y'', ``true'', ``t'', ``1'', ``on'', etc. as a
47 boolean true value, and ``no'', ``n'', ``false'', ``nil'', ``0'',
48 ``off'' as a boolean false value.
49
50 The following stanzas are used in the mke2fs.conf file. They will be
51 described in more detail in future sections of this document.
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53 [options]
54 Contains relations which influence how mke2fs behaves.
55
56 [defaults]
57 Contains relations which define the default parameters used by
58 mke2fs(8). In general, these defaults may be overridden by a
59 definition in the fs_types stanza, or by a command-line option
60 provided by the user.
61
62 [fs_types]
63 Contains relations which define defaults that should be used for
64 specific file system and usage types. The file system type and
65 usage type can be specified explicitly using the -tand-T options
66 to mke2fs(8), respectively.
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68 [devices]
69 Contains relations which define defaults for specific devices.
70
72 The following relations are defined in the [options] stanza.
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74 proceed_delay
75 If this relation is set to a positive integer, then mke2fs will
76 wait proceed_delay seconds after asking the user for permission
77 to proceed and then continue, even if the user has not answered
78 the question. Defaults to 0, which means to wait until the user
79 answers the question one way or another.
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81 sync_kludge
82 If this relation is set to a positive integer, then while writ‐
83 ing the inode table, mke2fs will request the operating system
84 flush out pending writes to initialize the inode table every
85 sync_kludge block groups. This is needed to work around buggy
86 kernels that don't handle writeback throttling correctly.
87
89 The following relations are defined in the [defaults] stanza.
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91 fs_type
92 This relation specifies the default filesystem type if the user
93 does not specify it via the -t option, or if mke2fs is not
94 started using a program name of the form mkfs.fs-type. If both
95 the user and the mke2fs.conf file do not specify a default
96 filesystem type, mke2fs will use a default filesystem type of
97 ext3 if a journal was requested via a command-line option, or
98 ext2 if not.
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100 undo_dir
101 This relation specifies the directory where the undo file should
102 be stored. It can be overridden via the E2FSPROGS_UNDO_DIR
103 environment variable. If the directory location is set to the
104 value none, mke2fs will not create an undo file.
105
106 In addition, any tags that can be specified in a per-file system tags
107 subsection as defined below (e.g., blocksize, hash_alg, inode_ratio,
108 inode_size, reserved_ratio, etc.) can also be specified in the defaults
109 stanza to specify the default value to be used if the user does not
110 specify one on the command line, and the filesystem-type specific sec‐
111 tion of the configuration file does not specify a default value.
112
114 Each tag in the [fs_types] stanza names a filesystem type or usage type
115 which can be specified via the -t or -T options to mke2fs(8), respec‐
116 tively.
117
118 The mke2fs program constructs a list of fs_types by concatenating the
119 filesystem type (i.e., ext2, ext3, etc.) with the usage type list. For
120 most configuration options, mke2fs will look for a subsection in the
121 [fs_types] stanza corresponding with each entry in the constructed
122 list, with later entries overriding earlier filesystem or usage types.
123 For example, consider the following mke2fs.conf fragment:
124
125 [defaults]
126 base_features = sparse_super,filetype,resize_inode,dir_index
127 blocksize = 4096
128 inode_size = 256
129 inode_ratio = 16384
130
131 [fs_types]
132 ext3 = {
133 features = has_journal
134 }
135 ext4 = {
136 features = extents,flex_bg
137 inode_size = 256
138 }
139 small = {
140 blocksize = 1024
141 inode_ratio = 4096
142 }
143 floppy = {
144 features = ^resize_inode
145 blocksize = 1024
146 inode_size = 128
147 }
148
149 If mke2fs started with a program name of mke2fs.ext4, then the filesys‐
150 tem type of ext4 will be used. If the filesystem is smaller than 3
151 megabytes, and no usage type is specified, then mke2fs will use a
152 default usage type of floppy. This results in an fs_types list of
153 "ext4, floppy". Both the ext4 subsection and the floppy subsection
154 define an inode_size relation, but since the later entries in the
155 fs_types list supersede earlier ones, the configuration parameter for
156 fs_types.floppy.inode_size will be used, so the filesystem will have
157 an inode size of 128.
158
159 The exception to this resolution is the features tag, which specifies a
160 set of changes to the features used by the filesystem, and which is
161 cumulative. So in the above example, first the configuration relation
162 defaults.base_features would enable an initial feature set with the
163 sparse_super, filetype, resize_inode, and dir_index features enabled.
164 Then configuration relation fs_types.ext4.features would enable the
165 extents and flex_bg features, and finally the configuration relation
166 fs_types.floppy.features would remove the resize_inode feature, result‐
167 ing in a filesystem feature set consisting of the sparse_super, file‐
168 type, dir_index, extents_and flex_bg features.
169
170 For each filesystem type, the following tags may be used in that
171 fs_type's subsection. These tags may also be used in the default sec‐
172 tion:
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174 base_features
175 This relation specifies the features which are initially enabled
176 for this filesystem type. Only one base_features will be used,
177 so if there are multiple entries in the fs_types list whose sub‐
178 sections define the base_features relation, only the last will
179 be used by mke2fs(8).
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181 enable_periodic_fsck
182 This boolean relation specifies whether periodic filesystem
183 checks should be enforced at boot time. If set to true, checks
184 will be forced every 180 days, or after a random number of
185 mounts. These values may be changed later via the -i and -c
186 command-line options to tune2fs(8).
187
188 errors Change the behavior of the kernel code when errors are detected.
189 In all cases, a filesystem error will cause e2fsck(8) to check
190 the filesystem on the next boot. errors can be one of the fol‐
191 lowing:
192
193 continue Continue normal execution.
194
195 remount-ro Remount filesystem read-only.
196
197 panic Cause a kernel panic.
198
199 features
200 This relation specifies a comma-separated list of features edit
201 requests which modify the feature set used by the newly con‐
202 structed filesystem. The syntax is the same as the -O command-
203 line option to mke2fs(8); that is, a feature can be prefixed by
204 a caret ('^') symbol to disable a named feature. Each feature
205 relation specified in the fs_types list will be applied in the
206 order found in the fs_types list.
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208 force_undo
209 This boolean relation, if set to a value of true, forces mke2fs
210 to always try to create an undo file, even if the undo file
211 might be huge and it might extend the time to create the
212 filesystem image because the inode table isn't being initialized
213 lazily.
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215 default_features
216 This relation specifies set of features which should be enabled
217 or disabled after applying the features listed in the base_fea‐
218 tures and features relations. It may be overridden by the -O
219 command-line option to mke2fs(8).
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221 auto_64-bit_support
222 This relation is a boolean which specifies whether mke2fs(8)
223 should automatically add the 64bit feature if the number of
224 blocks for the file system requires this feature to be enabled.
225 The resize_inode feature is also automatically disabled since it
226 doesn't support 64-bit block numbers.
227
228 default_mntopts
229 This relation specifies the set of mount options which should be
230 enabled by default. These may be changed at a later time with
231 the -o command-line option to tune2fs(8).
232
233 blocksize
234 This relation specifies the default blocksize if the user does
235 not specify a blocksize on the command line.
236
237 lazy_itable_init
238 This boolean relation specifies whether the inode table should
239 be lazily initialized. It only has meaning if the uninit_bg
240 feature is enabled. If lazy_itable_init is true and the
241 uninit_bg feature is enabled, the inode table will not be fully
242 initialized by mke2fs(8). This speeds up filesystem initializa‐
243 tion noticeably, but it requires the kernel to finish initializ‐
244 ing the filesystem in the background when the filesystem is
245 first mounted.
246
247 lazy_journal_init
248 This boolean relation specifies whether the journal inode should
249 be lazily initialized. It only has meaning if the has_journal
250 feature is enabled. If lazy_journal_init is true, the journal
251 inode will not be fully zeroed out by mke2fs. This speeds up
252 filesystem initialization noticeably, but carries some small
253 risk if the system crashes before the journal has been overwrit‐
254 ten entirely one time.
255
256 journal_location
257 This relation specifies the location of the journal.
258
259 num_backup_sb
260 This relation indicates whether file systems with the
261 sparse_super2 feature enabled should be created with 0, 1, or 2
262 backup superblocks.
263
264 packed_meta_blocks
265 This boolean relation specifies whether the allocation bitmaps,
266 inode table, and journal should be located at the beginning of
267 the file system.
268
269 inode_ratio
270 This relation specifies the default inode ratio if the user does
271 not specify one on the command line.
272
273 inode_size
274 This relation specifies the default inode size if the user does
275 not specify one on the command line.
276
277 reserved_ratio
278 This relation specifies the default percentage of filesystem
279 blocks reserved for the super-user, if the user does not specify
280 one on the command line.
281
282 hash_alg
283 This relation specifies the default hash algorithm used for the
284 new filesystems with hashed b-tree directories. Valid algo‐
285 rithms accepted are: legacy, half_md4, and tea.
286
287 flex_bg_size
288 This relation specifies the number of block groups that will be
289 packed together to create one large virtual block group on an
290 ext4 filesystem. This improves meta-data locality and perfor‐
291 mance on meta-data heavy workloads. The number of groups must
292 be a power of 2 and may only be specified if the flex_bg
293 filesystem feature is enabled.
294
295 options
296 This relation specifies additional extended options which should
297 be treated by mke2fs(8) as if they were prepended to the argu‐
298 ment of the -E option. This can be used to configure the
299 default extended options used by mke2fs(8) on a per-filesystem
300 type basis.
301
302 discard
303 This boolean relation specifies whether the mke2fs(8) should
304 attempt to discard device prior to filesystem creation.
305
306 cluster_size
307 This relation specifies the default cluster size if the bigalloc
308 file system feature is enabled. It can be overridden via the -C
309 command line option to mke2fs(8)
310
311 make_hugefiles
312 This boolean relation enables the creation of pre-allocated
313 files as part of formatting the file system. The extent tree
314 blocks for these pre-allocated files will be placed near the
315 beginning of the file system, so that if all of the other meta‐
316 data blocks are also configured to be placed near the beginning
317 of the file system (by disabling the backup superblocks, using
318 the packed_meta_blocks option, etc.), the data blocks of the
319 pre-allocated files will be contiguous.
320
321 hugefiles_dir
322 This relation specifies the directory where huge files are cre‐
323 ated, relative to the filesystem root.
324
325 hugefiles_uid
326 This relation controls the user ownership for all of the files
327 and directories created by the make_hugefiles feature.
328
329 hugefiles_gid
330 This relation controls the group ownership for all of the files
331 and directories created by the make_hugefiles feature.
332
333 hugefiles_umask
334 This relation specifies the umask used when creating the files
335 and directories by the make_hugefiles feature.
336
337 num_hugefiles
338 This relation specifies the number of huge files to be created.
339 If this relation is not specified, or is set to zero, and the
340 hugefiles_size relation is non-zero, then make_hugefiles will
341 create as many huge files as can fit to fill the entire file
342 system.
343
344 hugefiles_slack
345 This relation specifies how much space should be reserved for
346 other files.
347
348 hugefiles_size
349 This relation specifies the size of the huge files. If this
350 relation is not specified, the default is to fill the entire
351 file system.
352
353 hugefiles_align
354 This relation specifies the alignment for the start block of the
355 huge files. It also forces the size of huge files to be a mul‐
356 tiple of the requested alignment. If this relation is not spec‐
357 ified, no alignment requirement will be imposed on the huge
358 files.
359
360 hugefiles_align_disk
361 This relations specifies whether the alignment should be rela‐
362 tive to the beginning of the hard drive (assuming that the
363 starting offset of the partition is available to mke2fs). The
364 default value is false, which will cause hugefile alignment to
365 be relative to the beginning of the file system.
366
367 hugefiles_name
368 This relation specifies the base file name for the huge files.
369
370 hugefiles_digits
371 This relation specifies the (zero-padded) width of the field for
372 the huge file number.
373
374 zero_hugefiles
375 This boolean relation specifies whether or not zero blocks will
376 be written to the hugefiles while mke2fs(8) is creating them.
377 By default, zero blocks will be written to the huge files to
378 avoid stale data from being made available to potentially
379 untrusted user programs, unless the device supports a dis‐
380 card/trim operation which will take care of zeroing the device
381 blocks. By setting zero_hugefiles to false, this step will
382 always be skipped, which can be useful if it is known that the
383 disk has been previously erased, or if the user programs that
384 will have access to the huge files are trusted to not reveal
385 stale data.
386
387 encoding
388 This relation defines the file name encoding to be used if the
389 casefold feature is enabled. Currently the only valid encoding
390 is utf8-12.1 or utf8, which requests the most recent Unicode
391 version; since 12.1 is the only available Unicode version, utf8
392 and utf8-12.1 have the same result. encoding_flags This rela‐
393 tion defines encoding-specific flags. For utf8 encodings, the
394 only available flag is strict, which will cause attempts to cre‐
395 ate file names containing invalid Unicode characters to be
396 rejected by the kernel. Strict mode is not enabled by default.
397
399 Each tag in the [devices] stanza names device name so that per-device
400 defaults can be specified.
401
402 fs_type
403 This relation specifies the default parameter for the -t option,
404 if this option isn't specified on the command line.
405
406 usage_types
407 This relation specifies the default parameter for the -T option,
408 if this option isn't specified on the command line.
409
411 /etc/mke2fs.conf
412 The configuration file for mke2fs(8).
413
415 mke2fs(8)
416
417
418
419E2fsprogs version 1.45.6 March 2020 mke2fs.conf(5)