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 umask=### -- The permission mask (for files and directories, see umask(1)).
12 The default is the umask of current process.
13 dmask=### -- The permission mask for the directory.
14 The default is the umask of current process.
15 fmask=### -- The permission mask for files.
16 The default is the umask of current process.
17 codepage=### -- Sets the codepage for converting to shortname characters
18 on FAT and VFAT filesystems. By default, codepage 437
19 is used. This is the default for the U.S. and some
21 iocharset=name -- Character set to use for converting between 8 bit characters
22 and 16 bit Unicode characters. Long filenames are stored on
23 disk in Unicode format, but Unix for the most part doesn't
24 know how to deal with Unicode. There is also an option of
25 doing UTF8 translations with the utf8 option.
26 utf8=<bool> -- UTF8 is the filesystem safe version of Unicode that
27 is used by the console. It can be be enabled for the
28 filesystem with this option. If 'uni_xlate' gets set,
30 uni_xlate=<bool> -- Translate unhandled Unicode characters to special
31 escaped sequences. This would let you backup and
32 restore filenames that are created with any Unicode
33 characters. Until Linux supports Unicode for real,
34 this gives you an alternative. Without this option,
35 a '?' is used when no translation is possible. The
36 escape character is ':' because it is otherwise
37 illegal on the vfat filesystem. The escape sequence
38 that gets used is ':' and the four digits of hexadecimal
40 nonumtail=<bool> -- When creating 8.3 aliases, normally the alias will
41 end in '~1' or tilde followed by some number. If this
42 option is set, then if the filename is
43 "longfilename.txt" and "longfile.txt" does not
44 currently exist in the directory, 'longfile.txt' will
45 be the short alias instead of 'longfi~1.txt'.
47 quiet -- Stops printing certain warning messages.
48 check=s|r|n -- Case sensitivity checking setting.
49 s: strict, case sensitive
50 r: relaxed, case insensitive
51 n: normal, default setting, currently case insensitive
53 shortname=lower|win95|winnt|mixed
54 -- Shortname display/create setting.
55 lower: convert to lowercase for display,
56 emulate the Windows 95 rule for create.
57 win95: emulate the Windows 95 rule for display/create.
58 winnt: emulate the Windows NT rule for display/create.
59 mixed: emulate the Windows NT rule for display,
60 emulate the Windows 95 rule for create.
61 Default setting is `lower'.
63 <bool>: 0,1,yes,no,true,false
66 ----------------------------------------------------------------------
67 * Need to get rid of the raw scanning stuff. Instead, always use
68 a get next directory entry approach. The only thing left that uses
69 raw scanning is the directory renaming code.
73 ----------------------------------------------------------------------
74 * vfat_valid_longname does not properly checked reserved names.
75 * When a volume name is the same as a directory name in the root
76 directory of the filesystem, the directory name sometimes shows
78 * autoconv option does not work correctly.
81 ----------------------------------------------------------------------
82 If you have trouble with the VFAT filesystem, mail bug reports to
83 chaffee@bmrc.cs.berkeley.edu. Please specify the filename
84 and the operation that gave you trouble.
87 ----------------------------------------------------------------------
88 If you plan to make any modifications to the vfat filesystem, please
89 get the test suite that comes with the vfat distribution at
91 http://bmrc.berkeley.edu/people/chaffee/vfat.html
93 This tests quite a few parts of the vfat filesystem and additional
94 tests for new features or untested features would be appreciated.
96 NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM
97 ----------------------------------------------------------------------
98 (This documentation was provided by Galen C. Hunt <gchunt@cs.rochester.edu>
99 and lightly annotated by Gordon Chaffee).
101 This document presents a very rough, technical overview of my
102 knowledge of the extended FAT file system used in Windows NT 3.5 and
103 Windows 95. I don't guarantee that any of the following is correct,
104 but it appears to be so.
106 The extended FAT file system is almost identical to the FAT
107 file system used in DOS versions up to and including 6.223410239847
108 :-). The significant change has been the addition of long file names.
109 These names support up to 255 characters including spaces and lower
110 case characters as opposed to the traditional 8.3 short names.
112 Here is the description of the traditional FAT entry in the current
113 Windows 95 filesystem:
115 struct directory { // Short 8.3 names
116 unsigned char name[8]; // file name
117 unsigned char ext[3]; // file extension
118 unsigned char attr; // attribute byte
119 unsigned char lcase; // Case for base and extension
120 unsigned char ctime_ms; // Creation time, milliseconds
121 unsigned char ctime[2]; // Creation time
122 unsigned char cdate[2]; // Creation date
123 unsigned char adate[2]; // Last access date
124 unsigned char reserved[2]; // reserved values (ignored)
125 unsigned char time[2]; // time stamp
126 unsigned char date[2]; // date stamp
127 unsigned char start[2]; // starting cluster number
128 unsigned char size[4]; // size of the file
131 The lcase field specifies if the base and/or the extension of an 8.3
132 name should be capitalized. This field does not seem to be used by
133 Windows 95 but it is used by Windows NT. The case of filenames is not
134 completely compatible from Windows NT to Windows 95. It is not completely
135 compatible in the reverse direction, however. Filenames that fit in
136 the 8.3 namespace and are written on Windows NT to be lowercase will
137 show up as uppercase on Windows 95.
139 Note that the "start" and "size" values are actually little
140 endian integer values. The descriptions of the fields in this
141 structure are public knowledge and can be found elsewhere.
143 With the extended FAT system, Microsoft has inserted extra
144 directory entries for any files with extended names. (Any name which
145 legally fits within the old 8.3 encoding scheme does not have extra
146 entries.) I call these extra entries slots. Basically, a slot is a
147 specially formatted directory entry which holds up to 13 characters of
148 a file's extended name. Think of slots as additional labeling for the
149 directory entry of the file to which they correspond. Microsoft
150 prefers to refer to the 8.3 entry for a file as its alias and the
151 extended slot directory entries as the file name.
153 The C structure for a slot directory entry follows:
155 struct slot { // Up to 13 characters of a long name
156 unsigned char id; // sequence number for slot
157 unsigned char name0_4[10]; // first 5 characters in name
158 unsigned char attr; // attribute byte
159 unsigned char reserved; // always 0
160 unsigned char alias_checksum; // checksum for 8.3 alias
161 unsigned char name5_10[12]; // 6 more characters in name
162 unsigned char start[2]; // starting cluster number
163 unsigned char name11_12[4]; // last 2 characters in name
166 If the layout of the slots looks a little odd, it's only
167 because of Microsoft's efforts to maintain compatibility with old
168 software. The slots must be disguised to prevent old software from
169 panicking. To this end, a number of measures are taken:
171 1) The attribute byte for a slot directory entry is always set
172 to 0x0f. This corresponds to an old directory entry with
173 attributes of "hidden", "system", "read-only", and "volume
174 label". Most old software will ignore any directory
175 entries with the "volume label" bit set. Real volume label
176 entries don't have the other three bits set.
178 2) The starting cluster is always set to 0, an impossible
179 value for a DOS file.
181 Because the extended FAT system is backward compatible, it is
182 possible for old software to modify directory entries. Measures must
183 be taken to ensure the validity of slots. An extended FAT system can
184 verify that a slot does in fact belong to an 8.3 directory entry by
187 1) Positioning. Slots for a file always immediately proceed
188 their corresponding 8.3 directory entry. In addition, each
189 slot has an id which marks its order in the extended file
190 name. Here is a very abbreviated view of an 8.3 directory
191 entry and its corresponding long name slots for the file
192 "My Big File.Extension which is long":
194 <proceeding files...>
195 <slot #3, id = 0x43, characters = "h is long">
196 <slot #2, id = 0x02, characters = "xtension whic">
197 <slot #1, id = 0x01, characters = "My Big File.E">
198 <directory entry, name = "MYBIGFIL.EXT">
200 Note that the slots are stored from last to first. Slots
201 are numbered from 1 to N. The Nth slot is or'ed with 0x40
202 to mark it as the last one.
204 2) Checksum. Each slot has an "alias_checksum" value. The
205 checksum is calculated from the 8.3 name using the
208 for (sum = i = 0; i < 11; i++) {
209 sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + name[i]
212 3) If there is free space in the final slot, a Unicode NULL (0x0000)
213 is stored after the final character. After that, all unused
214 characters in the final slot are set to Unicode 0xFFFF.
216 Finally, note that the extended name is stored in Unicode. Each Unicode
217 character takes two bytes.