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 file systems.
12
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 be‐
18 low:
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.
67
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.
80
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 creator_os
92 This relation specifies the "creator operating system" for the
93 file system unless it is overridden on the command line. The
94 default value is the OS for which the mke2fs executable was com‐
95 piled.
96
97 fs_type
98 This relation specifies the default file system type if the user
99 does not specify it via the -t option, or if mke2fs is not
100 started using a program name of the form mkfs.fs-type. If both
101 the user and the mke2fs.conf file do not specify a default file
102 system type, mke2fs will use a default file system type of ext3
103 if a journal was requested via a command-line option, or ext2 if
104 not.
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106 undo_dir
107 This relation specifies the directory where the undo file should
108 be stored. It can be overridden via the E2FSPROGS_UNDO_DIR en‐
109 vironment variable. If the directory location is set to the
110 value none, mke2fs will not create an undo file.
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112 In addition, any tags that can be specified in a per-file system tags
113 subsection as defined below (e.g., blocksize, hash_alg, inode_ratio,
114 inode_size, reserved_ratio, etc.) can also be specified in the defaults
115 stanza to specify the default value to be used if the user does not
116 specify one on the command line, and the file system-type specific sec‐
117 tion of the configuration file does not specify a default value.
118
120 Each tag in the [fs_types] stanza names a file system type or usage
121 type which can be specified via the -t or -T options to mke2fs(8), re‐
122 spectively.
123
124 The mke2fs program constructs a list of fs_types by concatenating the
125 file system type (i.e., ext2, ext3, etc.) with the usage type list.
126 For most configuration options, mke2fs will look for a subsection in
127 the [fs_types] stanza corresponding with each entry in the constructed
128 list, with later entries overriding earlier file system or usage types.
129 For example, consider the following mke2fs.conf fragment:
130
131 [defaults]
132 base_features = sparse_super,filetype,resize_inode,dir_index
133 blocksize = 4096
134 inode_size = 256
135 inode_ratio = 16384
136
137 [fs_types]
138 ext3 = {
139 features = has_journal
140 }
141 ext4 = {
142 features = extents,flex_bg
143 inode_size = 256
144 }
145 small = {
146 blocksize = 1024
147 inode_ratio = 4096
148 }
149 floppy = {
150 features = ^resize_inode
151 blocksize = 1024
152 inode_size = 128
153 }
154
155 If mke2fs started with a program name of mke2fs.ext4, then the file
156 system type of ext4 will be used. If the file system is smaller than 3
157 megabytes, and no usage type is specified, then mke2fs will use a de‐
158 fault usage type of floppy. This results in an fs_types list of "ext4,
159 floppy". Both the ext4 subsection and the floppy subsection define an
160 inode_size relation, but since the later entries in the fs_types list
161 supersede earlier ones, the configuration parameter for
162 fs_types.floppy.inode_size will be used, so the file system will have
163 an inode size of 128.
164
165 The exception to this resolution is the features tag, which specifies a
166 set of changes to the features used by the file system, and which is
167 cumulative. So in the above example, first the configuration relation
168 defaults.base_features would enable an initial feature set with the
169 sparse_super, filetype, resize_inode, and dir_index features enabled.
170 Then configuration relation fs_types.ext4.features would enable the ex‐
171 tents and flex_bg features, and finally the configuration relation
172 fs_types.floppy.features would remove the resize_inode feature, result‐
173 ing in a file system feature set consisting of the sparse_super, file‐
174 type, dir_index, extents_and flex_bg features.
175
176 For each file system type, the following tags may be used in that
177 fs_type's subsection. These tags may also be used in the default sec‐
178 tion:
179
180 base_features
181 This relation specifies the features which are initially enabled
182 for this file system type. Only one base_features will be used,
183 so if there are multiple entries in the fs_types list whose sub‐
184 sections define the base_features relation, only the last will
185 be used by mke2fs(8).
186
187 enable_periodic_fsck
188 This boolean relation specifies whether periodic file system
189 checks should be enforced at boot time. If set to true, checks
190 will be forced every 180 days, or after a random number of
191 mounts. These values may be changed later via the -i and -c
192 command-line options to tune2fs(8).
193
194 errors Change the behavior of the kernel code when errors are detected.
195 In all cases, a file system error will cause e2fsck(8) to check
196 the file system on the next boot. errors can be one of the fol‐
197 lowing:
198
199 continue Continue normal execution.
200
201 remount-ro Remount file system read-only.
202
203 panic Cause a kernel panic.
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205 features
206 This relation specifies a comma-separated list of features edit
207 requests which modify the feature set used by the newly con‐
208 structed file system. The syntax is the same as the -O command-
209 line option to mke2fs(8); that is, a feature can be prefixed by
210 a caret ('^') symbol to disable a named feature. Each feature
211 relation specified in the fs_types list will be applied in the
212 order found in the fs_types list.
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214 force_undo
215 This boolean relation, if set to a value of true, forces mke2fs
216 to always try to create an undo file, even if the undo file
217 might be huge and it might extend the time to create the file
218 system image because the inode table isn't being initialized
219 lazily.
220
221 default_features
222 This relation specifies set of features which should be enabled
223 or disabled after applying the features listed in the base_fea‐
224 tures and features relations. It may be overridden by the -O
225 command-line option to mke2fs(8).
226
227 auto_64-bit_support
228 This relation is a boolean which specifies whether mke2fs(8)
229 should automatically add the 64bit feature if the number of
230 blocks for the file system requires this feature to be enabled.
231 The resize_inode feature is also automatically disabled since it
232 doesn't support 64-bit block numbers.
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234 default_mntopts
235 This relation specifies the set of mount options which should be
236 enabled by default. These may be changed at a later time with
237 the -o command-line option to tune2fs(8).
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239 blocksize
240 This relation specifies the default blocksize if the user does
241 not specify a blocksize on the command line.
242
243 lazy_itable_init
244 This boolean relation specifies whether the inode table should
245 be lazily initialized. It only has meaning if the uninit_bg
246 feature is enabled. If lazy_itable_init is true and the
247 uninit_bg feature is enabled, the inode table will not be fully
248 initialized by mke2fs(8). This speeds up file system initial‐
249 ization noticeably, but it requires the kernel to finish ini‐
250 tializing the file system in the background when the file system
251 is first mounted.
252
253 lazy_journal_init
254 This boolean relation specifies whether the journal inode should
255 be lazily initialized. It only has meaning if the has_journal
256 feature is enabled. If lazy_journal_init is true, the journal
257 inode will not be fully zeroed out by mke2fs. This speeds up
258 file system initialization noticeably, but carries some small
259 risk if the system crashes before the journal has been overwrit‐
260 ten entirely one time.
261
262 journal_location
263 This relation specifies the location of the journal.
264
265 num_backup_sb
266 This relation indicates whether file systems with the sparse_su‐
267 per2 feature enabled should be created with 0, 1, or 2 backup
268 superblocks.
269
270 packed_meta_blocks
271 This boolean relation specifies whether the allocation bitmaps,
272 inode table, and journal should be located at the beginning of
273 the file system.
274
275 inode_ratio
276 This relation specifies the default inode ratio if the user does
277 not specify one on the command line.
278
279 inode_size
280 This relation specifies the default inode size if the user does
281 not specify one on the command line.
282
283 reserved_ratio
284 This relation specifies the default percentage of file system
285 blocks reserved for the super-user, if the user does not specify
286 one on the command line.
287
288 hash_alg
289 This relation specifies the default hash algorithm used for the
290 new file systems with hashed b-tree directories. Valid algo‐
291 rithms accepted are: legacy, half_md4, and tea.
292
293 flex_bg_size
294 This relation specifies the number of block groups that will be
295 packed together to create one large virtual block group on an
296 ext4 file system. This improves meta-data locality and perfor‐
297 mance on meta-data heavy workloads. The number of groups must
298 be a power of 2 and may only be specified if the flex_bg file
299 system feature is enabled.
300
301 options
302 This relation specifies additional extended options which should
303 be treated by mke2fs(8) as if they were prepended to the argu‐
304 ment of the -E option. This can be used to configure the de‐
305 fault extended options used by mke2fs(8) on a per-file system
306 type basis.
307
308 discard
309 This boolean relation specifies whether the mke2fs(8) should at‐
310 tempt to discard device prior to file system creation.
311
312 cluster_size
313 This relation specifies the default cluster size if the bigalloc
314 file system feature is enabled. It can be overridden via the -C
315 command line option to mke2fs(8)
316
317 make_hugefiles
318 This boolean relation enables the creation of pre-allocated
319 files as part of formatting the file system. The extent tree
320 blocks for these pre-allocated files will be placed near the be‐
321 ginning of the file system, so that if all of the other metadata
322 blocks are also configured to be placed near the beginning of
323 the file system (by disabling the backup superblocks, using the
324 packed_meta_blocks option, etc.), the data blocks of the pre-al‐
325 located files will be contiguous.
326
327 hugefiles_dir
328 This relation specifies the directory where huge files are cre‐
329 ated, relative to the file system root.
330
331 hugefiles_uid
332 This relation controls the user ownership for all of the files
333 and directories created by the make_hugefiles feature.
334
335 hugefiles_gid
336 This relation controls the group ownership for all of the files
337 and directories created by the make_hugefiles feature.
338
339 hugefiles_umask
340 This relation specifies the umask used when creating the files
341 and directories by the make_hugefiles feature.
342
343 num_hugefiles
344 This relation specifies the number of huge files to be created.
345 If this relation is not specified, or is set to zero, and the
346 hugefiles_size relation is non-zero, then make_hugefiles will
347 create as many huge files as can fit to fill the entire file
348 system.
349
350 hugefiles_slack
351 This relation specifies how much space should be reserved for
352 other files.
353
354 hugefiles_size
355 This relation specifies the size of the huge files. If this re‐
356 lation is not specified, the default is to fill the entire file
357 system.
358
359 hugefiles_align
360 This relation specifies the alignment for the start block of the
361 huge files. It also forces the size of huge files to be a mul‐
362 tiple of the requested alignment. If this relation is not spec‐
363 ified, no alignment requirement will be imposed on the huge
364 files.
365
366 hugefiles_align_disk
367 This relations specifies whether the alignment should be rela‐
368 tive to the beginning of the hard drive (assuming that the
369 starting offset of the partition is available to mke2fs). The
370 default value is false, which will cause hugefile alignment to
371 be relative to the beginning of the file system.
372
373 hugefiles_name
374 This relation specifies the base file name for the huge files.
375
376 hugefiles_digits
377 This relation specifies the (zero-padded) width of the field for
378 the huge file number.
379
380 warn_y2038_dates
381 This boolean relation specifies whether mke2fs will issue a
382 warning when creating a file system with 128 byte inodes (and so
383 therefore will not support dates after January 19th, 2038). The
384 default value is true, except for file systems created for the
385 GNU Hurd since it only supports 128-byte inodes.
386
387 zero_hugefiles
388 This boolean relation specifies whether or not zero blocks will
389 be written to the hugefiles while mke2fs(8) is creating them.
390 By default, zero blocks will be written to the huge files to
391 avoid stale data from being made available to potentially un‐
392 trusted user programs, unless the device supports a discard/trim
393 operation which will take care of zeroing the device blocks. By
394 setting zero_hugefiles to false, this step will always be
395 skipped, which can be useful if it is known that the disk has
396 been previously erased, or if the user programs that will have
397 access to the huge files are trusted to not reveal stale data.
398
399 encoding
400 This relation defines the file name encoding to be used if the
401 casefold feature is enabled. Currently the only valid encoding
402 is utf8-12.1 or utf8, which requests the most recent Unicode
403 version; since 12.1 is the only available Unicode version, utf8
404 and utf8-12.1 have the same result. encoding_flags This rela‐
405 tion defines encoding-specific flags. For utf8 encodings, the
406 only available flag is strict, which will cause attempts to cre‐
407 ate file names containing invalid Unicode characters to be re‐
408 jected by the kernel. Strict mode is not enabled by default.
409
411 Each tag in the [devices] stanza names device name so that per-device
412 defaults can be specified.
413
414 fs_type
415 This relation specifies the default parameter for the -t option,
416 if this option isn't specified on the command line.
417
418 usage_types
419 This relation specifies the default parameter for the -T option,
420 if this option isn't specified on the command line.
421
423 /etc/mke2fs.conf
424 The configuration file for mke2fs(8).
425
427 mke2fs(8)
428
429
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431E2fsprogs version 1.47.0 February 2023 mke2fs.conf(5)