2 ----------------------------------------------------------------------
3 To use the vfat filesystem, use the filesystem type 'vfat'. i.e.
4 mount -t vfat /dev/fd0 /mnt
6 No special partition formatter is required. mkdosfs will work fine
7 if you want to format from within Linux.
10 ----------------------------------------------------------------------
11 uid=### -- Set the owner of all files on this filesystem.
12 The default is the uid of current process.
14 gid=### -- Set the group of all files on this filesystem.
15 The default is the gid of current process.
17 umask=### -- The permission mask (for files and directories, see umask(1)).
18 The default is the umask of current process.
20 dmask=### -- The permission mask for the directory.
21 The default is the umask of current process.
23 fmask=### -- The permission mask for files.
24 The default is the umask of current process.
26 allow_utime=### -- This option controls the permission check of mtime/atime.
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.
32 The default is set from `dmask' option. (If the directory is
33 writable, utime(2) is also allowed. I.e. ~dmask & 022)
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
41 codepage=### -- Sets the codepage number for converting to shortname
42 characters on FAT filesystem.
43 By default, FAT_DEFAULT_CODEPAGE setting is used.
45 iocharset=<name> -- Character set to use for converting between the
46 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.
52 There is also an option of doing UTF-8 translations
55 NOTE: "iocharset=utf8" is not recommended. If unsure,
56 you should consider the following option instead.
58 utf8=<bool> -- UTF-8 is the filesystem safe version of Unicode that
59 is used by the console. It can be enabled for the
60 filesystem with this option. If 'uni_xlate' gets set,
63 uni_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
74 nonumtail=<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'.
81 usefree -- 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.
88 quiet -- Stops printing certain warning messages.
90 check=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
95 nocase -- This was deprecated for vfat. Use shortname=win95 instead.
97 shortname=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'.
107 tz=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
110 (which Linux uses internally). This is particularly
111 useful when mounting devices (like digital cameras)
112 that are set to UTC in order to avoid the pitfalls of
115 showexec -- 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.
119 debug -- Can be set, but unused by the current implementation.
121 sys_immutable -- If set, ATTR_SYS attribute on FAT is handled as
122 IMMUTABLE flag on Linux. Not set by default.
124 flush -- If set, the filesystem will try to flush to disk more
125 early than normal. Not set by default.
127 <bool>: 0,1,yes,no,true,false
130 ----------------------------------------------------------------------
131 * Need to get rid of the raw scanning stuff. Instead, always use
132 a get next directory entry approach. The only thing left that uses
133 raw scanning is the directory renaming code.
137 ----------------------------------------------------------------------
138 * vfat_valid_longname does not properly checked reserved names.
139 * When a volume name is the same as a directory name in the root
140 directory of the filesystem, the directory name sometimes shows
142 * autoconv option does not work correctly.
145 ----------------------------------------------------------------------
146 If you have trouble with the VFAT filesystem, mail bug reports to
147 chaffee@bmrc.cs.berkeley.edu. Please specify the filename
148 and the operation that gave you trouble.
151 ----------------------------------------------------------------------
152 If you plan to make any modifications to the vfat filesystem, please
153 get the test suite that comes with the vfat distribution at
155 http://bmrc.berkeley.edu/people/chaffee/vfat.html
157 This tests quite a few parts of the vfat filesystem and additional
158 tests for new features or untested features would be appreciated.
160 NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM
161 ----------------------------------------------------------------------
162 (This documentation was provided by Galen C. Hunt <gchunt@cs.rochester.edu>
163 and lightly annotated by Gordon Chaffee).
165 This document presents a very rough, technical overview of my
166 knowledge of the extended FAT file system used in Windows NT 3.5 and
167 Windows 95. I don't guarantee that any of the following is correct,
168 but it appears to be so.
170 The extended FAT file system is almost identical to the FAT
171 file system used in DOS versions up to and including 6.223410239847
172 :-). The significant change has been the addition of long file names.
173 These names support up to 255 characters including spaces and lower
174 case characters as opposed to the traditional 8.3 short names.
176 Here is the description of the traditional FAT entry in the current
177 Windows 95 filesystem:
179 struct directory { // Short 8.3 names
180 unsigned char name[8]; // file name
181 unsigned char ext[3]; // file extension
182 unsigned char attr; // attribute byte
183 unsigned char lcase; // Case for base and extension
184 unsigned char ctime_ms; // Creation time, milliseconds
185 unsigned char ctime[2]; // Creation time
186 unsigned char cdate[2]; // Creation date
187 unsigned char adate[2]; // Last access date
188 unsigned char reserved[2]; // reserved values (ignored)
189 unsigned char time[2]; // time stamp
190 unsigned char date[2]; // date stamp
191 unsigned char start[2]; // starting cluster number
192 unsigned char size[4]; // size of the file
195 The lcase field specifies if the base and/or the extension of an 8.3
196 name should be capitalized. This field does not seem to be used by
197 Windows 95 but it is used by Windows NT. The case of filenames is not
198 completely compatible from Windows NT to Windows 95. It is not completely
199 compatible in the reverse direction, however. Filenames that fit in
200 the 8.3 namespace and are written on Windows NT to be lowercase will
201 show up as uppercase on Windows 95.
203 Note that the "start" and "size" values are actually little
204 endian integer values. The descriptions of the fields in this
205 structure are public knowledge and can be found elsewhere.
207 With the extended FAT system, Microsoft has inserted extra
208 directory entries for any files with extended names. (Any name which
209 legally fits within the old 8.3 encoding scheme does not have extra
210 entries.) I call these extra entries slots. Basically, a slot is a
211 specially formatted directory entry which holds up to 13 characters of
212 a file's extended name. Think of slots as additional labeling for the
213 directory entry of the file to which they correspond. Microsoft
214 prefers to refer to the 8.3 entry for a file as its alias and the
215 extended slot directory entries as the file name.
217 The C structure for a slot directory entry follows:
219 struct slot { // Up to 13 characters of a long name
220 unsigned char id; // sequence number for slot
221 unsigned char name0_4[10]; // first 5 characters in name
222 unsigned char attr; // attribute byte
223 unsigned char reserved; // always 0
224 unsigned char alias_checksum; // checksum for 8.3 alias
225 unsigned char name5_10[12]; // 6 more characters in name
226 unsigned char start[2]; // starting cluster number
227 unsigned char name11_12[4]; // last 2 characters in name
230 If the layout of the slots looks a little odd, it's only
231 because of Microsoft's efforts to maintain compatibility with old
232 software. The slots must be disguised to prevent old software from
233 panicking. To this end, a number of measures are taken:
235 1) The attribute byte for a slot directory entry is always set
236 to 0x0f. This corresponds to an old directory entry with
237 attributes of "hidden", "system", "read-only", and "volume
238 label". Most old software will ignore any directory
239 entries with the "volume label" bit set. Real volume label
240 entries don't have the other three bits set.
242 2) The starting cluster is always set to 0, an impossible
243 value for a DOS file.
245 Because the extended FAT system is backward compatible, it is
246 possible for old software to modify directory entries. Measures must
247 be taken to ensure the validity of slots. An extended FAT system can
248 verify that a slot does in fact belong to an 8.3 directory entry by
251 1) Positioning. Slots for a file always immediately proceed
252 their corresponding 8.3 directory entry. In addition, each
253 slot has an id which marks its order in the extended file
254 name. Here is a very abbreviated view of an 8.3 directory
255 entry and its corresponding long name slots for the file
256 "My Big File.Extension which is long":
258 <proceeding files...>
259 <slot #3, id = 0x43, characters = "h is long">
260 <slot #2, id = 0x02, characters = "xtension whic">
261 <slot #1, id = 0x01, characters = "My Big File.E">
262 <directory entry, name = "MYBIGFIL.EXT">
264 Note that the slots are stored from last to first. Slots
265 are numbered from 1 to N. The Nth slot is or'ed with 0x40
266 to mark it as the last one.
268 2) Checksum. Each slot has an "alias_checksum" value. The
269 checksum is calculated from the 8.3 name using the
272 for (sum = i = 0; i < 11; i++) {
273 sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + name[i]
276 3) If there is free space in the final slot, a Unicode NULL (0x0000)
277 is stored after the final character. After that, all unused
278 characters in the final slot are set to Unicode 0xFFFF.
280 Finally, note that the extended name is stored in Unicode. Each Unicode
281 character takes two bytes.