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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.
Paul Wise95523472009-08-01 21:30:31 +0900105 Default setting is `mixed'.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106
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
Matt LaPlante19f59462009-04-27 15:06:31 +0200127rodir -- FAT has the ATTR_RO (read-only) attribute. On Windows,
128 the ATTR_RO of the directory will just be ignored,
129 and is used only by applications as a flag (e.g. it's set
130 for the customized folder).
OGAWA Hirofumidfc209c2008-11-06 12:53:55 -0800131
132 If you want to use ATTR_RO as read-only flag even for
133 the directory, set this option.
134
Denis Karpov85c78592009-06-04 02:34:22 +0900135errors=panic|continue|remount-ro
136 -- specify FAT behavior on critical errors: panic, continue
137 without doing anything or remount the partition in
138 read-only mode (default behavior).
139
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140<bool>: 0,1,yes,no,true,false
141
142TODO
143----------------------------------------------------------------------
144* Need to get rid of the raw scanning stuff. Instead, always use
145 a get next directory entry approach. The only thing left that uses
146 raw scanning is the directory renaming code.
147
148
149POSSIBLE PROBLEMS
150----------------------------------------------------------------------
151* vfat_valid_longname does not properly checked reserved names.
152* When a volume name is the same as a directory name in the root
153 directory of the filesystem, the directory name sometimes shows
154 up as an empty file.
155* autoconv option does not work correctly.
156
157BUG REPORTS
158----------------------------------------------------------------------
159If you have trouble with the VFAT filesystem, mail bug reports to
160chaffee@bmrc.cs.berkeley.edu. Please specify the filename
161and the operation that gave you trouble.
162
163TEST SUITE
164----------------------------------------------------------------------
165If you plan to make any modifications to the vfat filesystem, please
166get the test suite that comes with the vfat distribution at
167
168 http://bmrc.berkeley.edu/people/chaffee/vfat.html
169
170This tests quite a few parts of the vfat filesystem and additional
171tests for new features or untested features would be appreciated.
172
173NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM
174----------------------------------------------------------------------
175(This documentation was provided by Galen C. Hunt <gchunt@cs.rochester.edu>
176 and lightly annotated by Gordon Chaffee).
177
178This document presents a very rough, technical overview of my
179knowledge of the extended FAT file system used in Windows NT 3.5 and
180Windows 95. I don't guarantee that any of the following is correct,
181but it appears to be so.
182
183The extended FAT file system is almost identical to the FAT
184file system used in DOS versions up to and including 6.223410239847
185:-). The significant change has been the addition of long file names.
186These names support up to 255 characters including spaces and lower
187case characters as opposed to the traditional 8.3 short names.
188
189Here is the description of the traditional FAT entry in the current
190Windows 95 filesystem:
191
192 struct directory { // Short 8.3 names
193 unsigned char name[8]; // file name
194 unsigned char ext[3]; // file extension
195 unsigned char attr; // attribute byte
196 unsigned char lcase; // Case for base and extension
197 unsigned char ctime_ms; // Creation time, milliseconds
198 unsigned char ctime[2]; // Creation time
199 unsigned char cdate[2]; // Creation date
200 unsigned char adate[2]; // Last access date
201 unsigned char reserved[2]; // reserved values (ignored)
202 unsigned char time[2]; // time stamp
203 unsigned char date[2]; // date stamp
204 unsigned char start[2]; // starting cluster number
205 unsigned char size[4]; // size of the file
206 };
207
208The lcase field specifies if the base and/or the extension of an 8.3
209name should be capitalized. This field does not seem to be used by
210Windows 95 but it is used by Windows NT. The case of filenames is not
211completely compatible from Windows NT to Windows 95. It is not completely
212compatible in the reverse direction, however. Filenames that fit in
213the 8.3 namespace and are written on Windows NT to be lowercase will
214show up as uppercase on Windows 95.
215
216Note that the "start" and "size" values are actually little
217endian integer values. The descriptions of the fields in this
218structure are public knowledge and can be found elsewhere.
219
220With the extended FAT system, Microsoft has inserted extra
221directory entries for any files with extended names. (Any name which
222legally fits within the old 8.3 encoding scheme does not have extra
223entries.) I call these extra entries slots. Basically, a slot is a
224specially formatted directory entry which holds up to 13 characters of
225a file's extended name. Think of slots as additional labeling for the
226directory entry of the file to which they correspond. Microsoft
227prefers to refer to the 8.3 entry for a file as its alias and the
228extended slot directory entries as the file name.
229
230The C structure for a slot directory entry follows:
231
232 struct slot { // Up to 13 characters of a long name
233 unsigned char id; // sequence number for slot
234 unsigned char name0_4[10]; // first 5 characters in name
235 unsigned char attr; // attribute byte
236 unsigned char reserved; // always 0
237 unsigned char alias_checksum; // checksum for 8.3 alias
238 unsigned char name5_10[12]; // 6 more characters in name
239 unsigned char start[2]; // starting cluster number
240 unsigned char name11_12[4]; // last 2 characters in name
241 };
242
243If the layout of the slots looks a little odd, it's only
244because of Microsoft's efforts to maintain compatibility with old
245software. The slots must be disguised to prevent old software from
246panicking. To this end, a number of measures are taken:
247
248 1) The attribute byte for a slot directory entry is always set
249 to 0x0f. This corresponds to an old directory entry with
250 attributes of "hidden", "system", "read-only", and "volume
251 label". Most old software will ignore any directory
252 entries with the "volume label" bit set. Real volume label
253 entries don't have the other three bits set.
254
255 2) The starting cluster is always set to 0, an impossible
256 value for a DOS file.
257
258Because the extended FAT system is backward compatible, it is
259possible for old software to modify directory entries. Measures must
260be taken to ensure the validity of slots. An extended FAT system can
261verify that a slot does in fact belong to an 8.3 directory entry by
262the following:
263
264 1) Positioning. Slots for a file always immediately proceed
265 their corresponding 8.3 directory entry. In addition, each
266 slot has an id which marks its order in the extended file
267 name. Here is a very abbreviated view of an 8.3 directory
268 entry and its corresponding long name slots for the file
269 "My Big File.Extension which is long":
270
271 <proceeding files...>
272 <slot #3, id = 0x43, characters = "h is long">
273 <slot #2, id = 0x02, characters = "xtension whic">
274 <slot #1, id = 0x01, characters = "My Big File.E">
275 <directory entry, name = "MYBIGFIL.EXT">
276
277 Note that the slots are stored from last to first. Slots
278 are numbered from 1 to N. The Nth slot is or'ed with 0x40
279 to mark it as the last one.
280
281 2) Checksum. Each slot has an "alias_checksum" value. The
282 checksum is calculated from the 8.3 name using the
283 following algorithm:
284
285 for (sum = i = 0; i < 11; i++) {
286 sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + name[i]
287 }
288
289 3) If there is free space in the final slot, a Unicode NULL (0x0000)
290 is stored after the final character. After that, all unused
291 characters in the final slot are set to Unicode 0xFFFF.
292
293Finally, note that the extended name is stored in Unicode. Each Unicode
294character takes two bytes.