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Linus Torvalds1da177e2005-04-16 15:20:36 -07001USING VFAT
2----------------------------------------------------------------------
3To use the vfat filesystem, use the filesystem type 'vfat'. i.e.
4 mount -t vfat /dev/fd0 /mnt
5
6No special partition formatter is required. mkdosfs will work fine
7if you want to format from within Linux.
8
9VFAT MOUNT OPTIONS
10----------------------------------------------------------------------
Bart Trojanowski8986ab52008-11-06 12:53:44 -080011uid=### -- Set the owner of all files on this filesystem.
12 The default is the uid of current process.
13
14gid=### -- Set the group of all files on this filesystem.
15 The default is the gid of current process.
16
Linus Torvalds1da177e2005-04-16 15:20:36 -070017umask=### -- The permission mask (for files and directories, see umask(1)).
18 The default is the umask of current process.
19
20dmask=### -- The permission mask for the directory.
21 The default is the umask of current process.
22
23fmask=### -- The permission mask for files.
24 The default is the umask of current process.
25
OGAWA Hirofumi1ae43f82008-04-28 02:16:26 -070026allow_utime=### -- This option controls the permission check of mtime/atime.
27
28 20 - If current process is in group of file's group ID,
29 you can change timestamp.
30 2 - Other users can change timestamp.
31
32 The default is set from `dmask' option. (If the directory is
33 writable, utime(2) is also allowed. I.e. ~dmask & 022)
34
35 Normally utime(2) checks current process is owner of
36 the file, or it has CAP_FOWNER capability. But FAT
37 filesystem doesn't have uid/gid on disk, so normal
38 check is too unflexible. With this option you can
39 relax it.
40
Linus Torvalds1da177e2005-04-16 15:20:36 -070041codepage=### -- Sets the codepage number for converting to shortname
42 characters on FAT filesystem.
43 By default, FAT_DEFAULT_CODEPAGE setting is used.
44
Bart Trojanowski8986ab52008-11-06 12:53:44 -080045iocharset=<name> -- Character set to use for converting between the
Linus Torvalds1da177e2005-04-16 15:20:36 -070046 encoding is used for user visible filename and 16 bit
47 Unicode characters. Long filenames are stored on disk
48 in Unicode format, but Unix for the most part doesn't
49 know how to deal with Unicode.
50 By default, FAT_DEFAULT_IOCHARSET setting is used.
51
Alexey Dobriyan4de151d2006-03-22 00:13:35 +010052 There is also an option of doing UTF-8 translations
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 with the utf8 option.
54
55 NOTE: "iocharset=utf8" is not recommended. If unsure,
56 you should consider the following option instead.
57
Alexey Dobriyan4de151d2006-03-22 00:13:35 +010058utf8=<bool> -- UTF-8 is the filesystem safe version of Unicode that
Paolo Ornati670e9f32006-10-03 22:57:56 +020059 is used by the console. It can be enabled for the
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 filesystem with this option. If 'uni_xlate' gets set,
Alexey Dobriyan4de151d2006-03-22 00:13:35 +010061 UTF-8 gets disabled.
Linus Torvalds1da177e2005-04-16 15:20:36 -070062
63uni_xlate=<bool> -- Translate unhandled Unicode characters to special
64 escaped sequences. This would let you backup and
65 restore filenames that are created with any Unicode
66 characters. Until Linux supports Unicode for real,
67 this gives you an alternative. Without this option,
68 a '?' is used when no translation is possible. The
69 escape character is ':' because it is otherwise
70 illegal on the vfat filesystem. The escape sequence
71 that gets used is ':' and the four digits of hexadecimal
72 unicode.
73
74nonumtail=<bool> -- When creating 8.3 aliases, normally the alias will
75 end in '~1' or tilde followed by some number. If this
76 option is set, then if the filename is
77 "longfilename.txt" and "longfile.txt" does not
78 currently exist in the directory, 'longfile.txt' will
79 be the short alias instead of 'longfi~1.txt'.
80
OGAWA Hirofumi28ec0392007-05-08 00:31:01 -070081usefree -- Use the "free clusters" value stored on FSINFO. It'll
82 be used to determine number of free clusters without
83 scanning disk. But it's not used by default, because
84 recent Windows don't update it correctly in some
85 case. If you are sure the "free clusters" on FSINFO is
86 correct, by this option you can avoid scanning disk.
87
Linus Torvalds1da177e2005-04-16 15:20:36 -070088quiet -- Stops printing certain warning messages.
89
90check=s|r|n -- Case sensitivity checking setting.
91 s: strict, case sensitive
92 r: relaxed, case insensitive
93 n: normal, default setting, currently case insensitive
94
Bart Trojanowski8986ab52008-11-06 12:53:44 -080095nocase -- This was deprecated for vfat. Use shortname=win95 instead.
96
Linus Torvalds1da177e2005-04-16 15:20:36 -070097shortname=lower|win95|winnt|mixed
98 -- Shortname display/create setting.
99 lower: convert to lowercase for display,
100 emulate the Windows 95 rule for create.
101 win95: emulate the Windows 95 rule for display/create.
102 winnt: emulate the Windows NT rule for display/create.
103 mixed: emulate the Windows NT rule for display,
104 emulate the Windows 95 rule for create.
105 Default setting is `lower'.
106
Joe Peterson41003cd2008-07-25 01:46:48 -0700107tz=UTC -- Interpret timestamps as UTC rather than local time.
108 This option disables the conversion of timestamps
109 between local time (as used by Windows on FAT) and UTC
Bart Trojanowski8986ab52008-11-06 12:53:44 -0800110 (which Linux uses internally). This is particularly
Joe Peterson41003cd2008-07-25 01:46:48 -0700111 useful when mounting devices (like digital cameras)
112 that are set to UTC in order to avoid the pitfalls of
113 local time.
114
Bart Trojanowski8986ab52008-11-06 12:53:44 -0800115showexec -- If set, the execute permission bits of the file will be
116 allowed only if the extension part of the name is .EXE,
117 .COM, or .BAT. Not set by default.
118
119debug -- Can be set, but unused by the current implementation.
120
121sys_immutable -- If set, ATTR_SYS attribute on FAT is handled as
122 IMMUTABLE flag on Linux. Not set by default.
123
124flush -- If set, the filesystem will try to flush to disk more
125 early than normal. Not set by default.
126
OGAWA Hirofumidfc209c2008-11-06 12:53:55 -0800127rodir -- FAT has the ATTR_RO (read-only) attribute. But on Windows,
128 the ATTR_RO of the directory will be just ignored actually,
129 and is used by only applications as flag. E.g. it's setted
130 for the customized folder.
131
132 If you want to use ATTR_RO as read-only flag even for
133 the directory, set this option.
134
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135<bool>: 0,1,yes,no,true,false
136
137TODO
138----------------------------------------------------------------------
139* Need to get rid of the raw scanning stuff. Instead, always use
140 a get next directory entry approach. The only thing left that uses
141 raw scanning is the directory renaming code.
142
143
144POSSIBLE PROBLEMS
145----------------------------------------------------------------------
146* vfat_valid_longname does not properly checked reserved names.
147* When a volume name is the same as a directory name in the root
148 directory of the filesystem, the directory name sometimes shows
149 up as an empty file.
150* autoconv option does not work correctly.
151
152BUG REPORTS
153----------------------------------------------------------------------
154If you have trouble with the VFAT filesystem, mail bug reports to
155chaffee@bmrc.cs.berkeley.edu. Please specify the filename
156and the operation that gave you trouble.
157
158TEST SUITE
159----------------------------------------------------------------------
160If you plan to make any modifications to the vfat filesystem, please
161get the test suite that comes with the vfat distribution at
162
163 http://bmrc.berkeley.edu/people/chaffee/vfat.html
164
165This tests quite a few parts of the vfat filesystem and additional
166tests for new features or untested features would be appreciated.
167
168NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM
169----------------------------------------------------------------------
170(This documentation was provided by Galen C. Hunt <gchunt@cs.rochester.edu>
171 and lightly annotated by Gordon Chaffee).
172
173This document presents a very rough, technical overview of my
174knowledge of the extended FAT file system used in Windows NT 3.5 and
175Windows 95. I don't guarantee that any of the following is correct,
176but it appears to be so.
177
178The extended FAT file system is almost identical to the FAT
179file system used in DOS versions up to and including 6.223410239847
180:-). The significant change has been the addition of long file names.
181These names support up to 255 characters including spaces and lower
182case characters as opposed to the traditional 8.3 short names.
183
184Here is the description of the traditional FAT entry in the current
185Windows 95 filesystem:
186
187 struct directory { // Short 8.3 names
188 unsigned char name[8]; // file name
189 unsigned char ext[3]; // file extension
190 unsigned char attr; // attribute byte
191 unsigned char lcase; // Case for base and extension
192 unsigned char ctime_ms; // Creation time, milliseconds
193 unsigned char ctime[2]; // Creation time
194 unsigned char cdate[2]; // Creation date
195 unsigned char adate[2]; // Last access date
196 unsigned char reserved[2]; // reserved values (ignored)
197 unsigned char time[2]; // time stamp
198 unsigned char date[2]; // date stamp
199 unsigned char start[2]; // starting cluster number
200 unsigned char size[4]; // size of the file
201 };
202
203The lcase field specifies if the base and/or the extension of an 8.3
204name should be capitalized. This field does not seem to be used by
205Windows 95 but it is used by Windows NT. The case of filenames is not
206completely compatible from Windows NT to Windows 95. It is not completely
207compatible in the reverse direction, however. Filenames that fit in
208the 8.3 namespace and are written on Windows NT to be lowercase will
209show up as uppercase on Windows 95.
210
211Note that the "start" and "size" values are actually little
212endian integer values. The descriptions of the fields in this
213structure are public knowledge and can be found elsewhere.
214
215With the extended FAT system, Microsoft has inserted extra
216directory entries for any files with extended names. (Any name which
217legally fits within the old 8.3 encoding scheme does not have extra
218entries.) I call these extra entries slots. Basically, a slot is a
219specially formatted directory entry which holds up to 13 characters of
220a file's extended name. Think of slots as additional labeling for the
221directory entry of the file to which they correspond. Microsoft
222prefers to refer to the 8.3 entry for a file as its alias and the
223extended slot directory entries as the file name.
224
225The C structure for a slot directory entry follows:
226
227 struct slot { // Up to 13 characters of a long name
228 unsigned char id; // sequence number for slot
229 unsigned char name0_4[10]; // first 5 characters in name
230 unsigned char attr; // attribute byte
231 unsigned char reserved; // always 0
232 unsigned char alias_checksum; // checksum for 8.3 alias
233 unsigned char name5_10[12]; // 6 more characters in name
234 unsigned char start[2]; // starting cluster number
235 unsigned char name11_12[4]; // last 2 characters in name
236 };
237
238If the layout of the slots looks a little odd, it's only
239because of Microsoft's efforts to maintain compatibility with old
240software. The slots must be disguised to prevent old software from
241panicking. To this end, a number of measures are taken:
242
243 1) The attribute byte for a slot directory entry is always set
244 to 0x0f. This corresponds to an old directory entry with
245 attributes of "hidden", "system", "read-only", and "volume
246 label". Most old software will ignore any directory
247 entries with the "volume label" bit set. Real volume label
248 entries don't have the other three bits set.
249
250 2) The starting cluster is always set to 0, an impossible
251 value for a DOS file.
252
253Because the extended FAT system is backward compatible, it is
254possible for old software to modify directory entries. Measures must
255be taken to ensure the validity of slots. An extended FAT system can
256verify that a slot does in fact belong to an 8.3 directory entry by
257the following:
258
259 1) Positioning. Slots for a file always immediately proceed
260 their corresponding 8.3 directory entry. In addition, each
261 slot has an id which marks its order in the extended file
262 name. Here is a very abbreviated view of an 8.3 directory
263 entry and its corresponding long name slots for the file
264 "My Big File.Extension which is long":
265
266 <proceeding files...>
267 <slot #3, id = 0x43, characters = "h is long">
268 <slot #2, id = 0x02, characters = "xtension whic">
269 <slot #1, id = 0x01, characters = "My Big File.E">
270 <directory entry, name = "MYBIGFIL.EXT">
271
272 Note that the slots are stored from last to first. Slots
273 are numbered from 1 to N. The Nth slot is or'ed with 0x40
274 to mark it as the last one.
275
276 2) Checksum. Each slot has an "alias_checksum" value. The
277 checksum is calculated from the 8.3 name using the
278 following algorithm:
279
280 for (sum = i = 0; i < 11; i++) {
281 sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + name[i]
282 }
283
284 3) If there is free space in the final slot, a Unicode NULL (0x0000)
285 is stored after the final character. After that, all unused
286 characters in the final slot are set to Unicode 0xFFFF.
287
288Finally, note that the extended name is stored in Unicode. Each Unicode
289character takes two bytes.