1 ====
2 VFAT
3 ====
4
5 USING VFAT
6 ==========
7
8 To use the vfat filesystem, use the filesystem
9
10 mount -t vfat /dev/fd0 /mnt
11
12
13 No special partition formatter is required,
14 'mkdosfs' will work fine if you want to format
15
16 VFAT MOUNT OPTIONS
17 ==================
18
19 **uid=###**
20 Set the owner of all files on this fil
21 The default is the uid of current proc
22
23 **gid=###**
24 Set the group of all files on this fil
25 The default is the gid of current proc
26
27 **umask=###**
28 The permission mask (for files and dir
29 The default is the umask of current pr
30
31 **dmask=###**
32 The permission mask for the directory.
33 The default is the umask of current pr
34
35 **fmask=###**
36 The permission mask for files.
37 The default is the umask of current pr
38
39 **allow_utime=###**
40 This option controls the permission ch
41
42 **-20**: If current process is
43 you can change timestamp.
44
45 **-2**: Other users can change
46
47 The default is set from dmask option.
48 writable, utime(2) is also allowed. i.
49
50 Normally utime(2) checks current proce
51 the file, or it has CAP_FOWNER capabil
52 filesystem doesn't have uid/gid on dis
53 check is too inflexible. With this opt
54 relax it.
55
56 **codepage=###**
57 Sets the codepage number for convertin
58 characters on FAT filesystem.
59 By default, FAT_DEFAULT_CODEPAGE setti
60
61 **iocharset=<name>**
62 Character set to use for converting be
63 encoding is used for user visible file
64 Unicode characters. Long filenames are
65 in Unicode format, but Unix for the mo
66 know how to deal with Unicode.
67 By default, FAT_DEFAULT_IOCHARSET sett
68
69 There is also an option of doing UTF-8
70 with the utf8 option.
71
72 .. note:: ``iocharset=utf8`` is not recommende
73 the utf8 option instead.
74
75 **utf8=<bool>**
76 UTF-8 is the filesystem safe version o
77 is used by the console. It can be enab
78 for the filesystem with this option.
79 If 'uni_xlate' gets set, UTF-8 gets di
80 By default, FAT_DEFAULT_UTF8 setting i
81
82 **uni_xlate=<bool>**
83 Translate unhandled Unicode characters
84 escaped sequences. This would let you
85 restore filenames that are created wit
86 characters. Until Linux supports Unic
87 this gives you an alternative. Withou
88 a '?' is used when no translation is p
89 escape character is ':' because it is
90 illegal on the vfat filesystem. The e
91 that gets used is ':' and the four dig
92 unicode.
93
94 **nonumtail=<bool>**
95 When creating 8.3 aliases, normally th
96 end in '~1' or tilde followed by some
97 option is set, then if the filename is
98 "longfilename.txt" and "longfile.txt"
99 currently exist in the directory, long
100 be the short alias instead of longfi~1
101
102 **usefree**
103 Use the "free clusters" value stored o
104 be used to determine number of free cl
105 scanning disk. But it's not used by de
106 recent Windows don't update it correct
107 case. If you are sure the "free cluste
108 correct, by this option you can avoid
109
110 **quiet**
111 Stops printing certain warning message
112
113 **check=s|r|n**
114 Case sensitivity checking setting.
115
116 **s**: strict, case sensitive
117
118 **r**: relaxed, case insensitive
119
120 **n**: normal, default setting, curren
121
122 **nocase**
123 This was deprecated for vfat. Use ``sh
124
125 **shortname=lower|win95|winnt|mixed**
126 Shortname display/create setting.
127
128 **lower**: convert to lowercase for di
129 emulate the Windows 95 rule for create
130
131 **win95**: emulate the Windows 95 rule
132
133 **winnt**: emulate the Windows NT rule
134
135 **mixed**: emulate the Windows NT rule
136 emulate the Windows 95 rule for create
137
138 Default setting is `mixed`.
139
140 **tz=UTC**
141 Interpret timestamps as UTC rather tha
142 This option disables the conversion of
143 between local time (as used by Windows
144 (which Linux uses internally). This i
145 useful when mounting devices (like dig
146 that are set to UTC in order to avoid
147 local time.
148
149 **time_offset=minutes**
150 Set offset for conversion of timestamp
151 used by FAT to UTC. I.e. <minutes> min
152 from each timestamp to convert it to U
153 Linux. This is useful when time zone s
154 not the time zone used by the filesyst
155 option still does not provide correct
156 cases in presence of DST - time stamps
157 setting will be off by one hour.
158
159 **showexec**
160 If set, the execute permission bits of
161 allowed only if the extension part of
162 .COM, or .BAT. Not set by default.
163
164 **debug**
165 Can be set, but unused by the current
166
167 **sys_immutable**
168 If set, ATTR_SYS attribute on FAT is h
169 IMMUTABLE flag on Linux. Not set by de
170
171 **flush**
172 If set, the filesystem will try to flu
173 early than normal. Not set by default.
174
175 **rodir**
176 FAT has the ATTR_RO (read-only) attrib
177 the ATTR_RO of the directory will just
178 and is used only by applications as a
179 for the customized folder).
180
181 If you want to use ATTR_RO as read-onl
182 the directory, set this option.
183
184 **errors=panic|continue|remount-ro**
185 specify FAT behavior on critical error
186 without doing anything or remount the
187 read-only mode (default behavior).
188
189 **discard**
190 If set, issues discard/TRIM commands t
191 device when blocks are freed. This is
192 and sparse/thinly-provisioned LUNs.
193
194 **nfs=stale_rw|nostale_ro**
195 Enable this only if you want to export
196 over NFS.
197
198 **stale_rw**: This option main
199 *inodes* by *i_logstart* which
200 improve look-ups. Full file op
201 supported but with cache evict
202 result in ESTALE issues.
203
204 **nostale_ro**: This option ba
205 on the on-disk location of a f
206 This ensures that ESTALE will
207 evicted from the inode cache.
208 such as rename, create and unl
209 previously pointed at one file
210 potentially causing data corru
211 option also mounts the filesys
212
213 To maintain backward compatibility, ``
214 defaulting to "stale_rw".
215
216 **dos1xfloppy <bool>: 0,1,yes,no,true,false**
217 If set, use a fallback default BIOS Pa
218 configuration, determined by backing d
219 parameters match defaults assumed by D
220 180 kiB, 320 kiB, and 360 kiB floppies
221
222
223
224 LIMITATION
225 ==========
226
227 The fallocated region of file is discarded at
228 when using fallocate with FALLOC_FL_KEEP_SIZE.
229 So, User should assume that fallocated region
230 last close if there is memory pressure resulti
231 the inode from the memory. As a result, for an
232 the fallocated region, user should make sure t
233 after reopening the file.
234
235 TODO
236 ====
237 Need to get rid of the raw scanning stuff. In
238 a get next directory entry approach. The only
239 raw scanning is the directory renaming code.
240
241
242 POSSIBLE PROBLEMS
243 =================
244
245 - vfat_valid_longname does not properly checke
246 - When a volume name is the same as a director
247 directory of the filesystem, the directory n
248 up as an empty file.
249 - autoconv option does not work correctly.
250
251
252 TEST SUITE
253 ==========
254 If you plan to make any modifications to the v
255 get the test suite that comes with the vfat di
256
257 `<http://web.archive.org/web/*/http://bmrc.ber
258
259 This tests quite a few parts of the vfat files
260 tests for new features or untested features wo
261
262 NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM
263 =============================================
264 This documentation was provided by Galen C. Hu
265 lightly annotated by Gordon Chaffee.
266
267 This document presents a very rough, technical
268 knowledge of the extended FAT file system used
269 Windows 95. I don't guarantee that any of the
270 but it appears to be so.
271
272 The extended FAT file system is almost identic
273 file system used in DOS versions up to and inc
274 :-). The significant change has been the addi
275 These names support up to 255 characters inclu
276 case characters as opposed to the traditional
277
278 Here is the description of the traditional FAT
279 Windows 95 filesystem::
280
281 struct directory { // Short 8.3 names
282 unsigned char name[8];
283 unsigned char ext[3];
284 unsigned char attr;
285 unsigned char lcase;
286 unsigned char ctime_ms;
287 unsigned char ctime[2];
288 unsigned char cdate[2];
289 unsigned char adate[2];
290 unsigned char reserved[2];
291 unsigned char time[2];
292 unsigned char date[2];
293 unsigned char start[2];
294 unsigned char size[4];
295 };
296
297
298 The lcase field specifies if the base and/or t
299 name should be capitalized. This field does n
300 Windows 95 but it is used by Windows NT. The
301 completely compatible from Windows NT to Windo
302 compatible in the reverse direction, however.
303 the 8.3 namespace and are written on Windows N
304 show up as uppercase on Windows 95.
305
306 .. note:: Note that the ``start`` and ``size``
307 endian integer values. The descript
308 structure are public knowledge and c
309
310 With the extended FAT system, Microsoft has in
311 directory entries for any files with extended
312 legally fits within the old 8.3 encoding schem
313 entries.) I call these extra entries slots.
314 specially formatted directory entry which hold
315 a file's extended name. Think of slots as add
316 directory entry of the file to which they corr
317 prefers to refer to the 8.3 entry for a file a
318 extended slot directory entries as the file na
319
320 The C structure for a slot directory entry fol
321
322 struct slot { // Up to 13 characters o
323 unsigned char id;
324 unsigned char name0_4[10];
325 unsigned char attr;
326 unsigned char reserved;
327 unsigned char alias_checksum;
328 unsigned char name5_10[12];
329 unsigned char start[2];
330 unsigned char name11_12[4];
331 };
332
333
334 If the layout of the slots looks a little odd,
335 because of Microsoft's efforts to maintain com
336 software. The slots must be disguised to prev
337 panicking. To this end, a number of measures
338
339 1) The attribute byte for a slot direc
340 to 0x0f. This corresponds to an ol
341 attributes of "hidden", "system", "
342 label". Most old software will ign
343 entries with the "volume label" bit
344 entries don't have the other three
345
346 2) The starting cluster is always set
347 value for a DOS file.
348
349 Because the extended FAT system is backward co
350 possible for old software to modify directory
351 be taken to ensure the validity of slots. An
352 verify that a slot does in fact belong to an 8
353 the following:
354
355 1) Positioning. Slots for a file alwa
356 their corresponding 8.3 directory e
357 slot has an id which marks its orde
358 name. Here is a very abbreviated v
359 entry and its corresponding long na
360 "My Big File.Extension which is lon
361
362 <proceeding files...>
363 <slot #3, id = 0x43, character
364 <slot #2, id = 0x02, character
365 <slot #1, id = 0x01, character
366 <directory entry, name = "MYBI
367
368
369 .. note:: Note that the slots are s
370 are numbered from 1 to N.
371 0x40 to mark it as the la
372
373 2) Checksum. Each slot has an alias_c
374 checksum is calculated from the 8.3
375 following algorithm::
376
377 for (sum = i = 0; i < 11; i++)
378 sum = (((sum&1)<<7)|((
379 }
380
381
382 3) If there is free space in the final
383 is stored after the final character
384 characters in the final slot are se
385
386 Finally, note that the extended name is stored
387 character takes either two or four bytes, UTF-
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