1USING 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---------------------------------------------------------------------- 11uid=### -- 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 17umask=### -- 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 26allow_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 41codepage=### -- Sets the codepage number for converting to shortname 42 characters on FAT filesystem. 43 By default, FAT_DEFAULT_CODEPAGE setting is used. 44 45iocharset=<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. 51 52 There is also an option of doing UTF-8 translations 53 with the utf8 option. 54 55 NOTE: "iocharset=utf8" is not recommended. If unsure, 56 you should consider the following option instead. 57 58utf8=<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, 61 UTF-8 gets disabled. 62 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 81usefree -- 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 88quiet -- 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 95nocase -- This was deprecated for vfat. Use shortname=win95 instead. 96 97shortname=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 `mixed'. 106 107tz=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 113 local time. 114 115showexec -- 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 127rodir -- 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). 131 132 If you want to use ATTR_RO as read-only flag even for 133 the directory, set this option. 134 135errors=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). 139 140<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://web.archive.org/web/*/http://bmrc.berkeley.edu/ 169 people/chaffee/vfat.html 170 171This tests quite a few parts of the vfat filesystem and additional 172tests for new features or untested features would be appreciated. 173 174NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM 175---------------------------------------------------------------------- 176(This documentation was provided by Galen C. Hunt <gchunt@cs.rochester.edu> 177 and lightly annotated by Gordon Chaffee). 178 179This document presents a very rough, technical overview of my 180knowledge of the extended FAT file system used in Windows NT 3.5 and 181Windows 95. I don't guarantee that any of the following is correct, 182but it appears to be so. 183 184The extended FAT file system is almost identical to the FAT 185file system used in DOS versions up to and including 6.223410239847 186:-). The significant change has been the addition of long file names. 187These names support up to 255 characters including spaces and lower 188case characters as opposed to the traditional 8.3 short names. 189 190Here is the description of the traditional FAT entry in the current 191Windows 95 filesystem: 192 193 struct directory { // Short 8.3 names 194 unsigned char name[8]; // file name 195 unsigned char ext[3]; // file extension 196 unsigned char attr; // attribute byte 197 unsigned char lcase; // Case for base and extension 198 unsigned char ctime_ms; // Creation time, milliseconds 199 unsigned char ctime[2]; // Creation time 200 unsigned char cdate[2]; // Creation date 201 unsigned char adate[2]; // Last access date 202 unsigned char reserved[2]; // reserved values (ignored) 203 unsigned char time[2]; // time stamp 204 unsigned char date[2]; // date stamp 205 unsigned char start[2]; // starting cluster number 206 unsigned char size[4]; // size of the file 207 }; 208 209The lcase field specifies if the base and/or the extension of an 8.3 210name should be capitalized. This field does not seem to be used by 211Windows 95 but it is used by Windows NT. The case of filenames is not 212completely compatible from Windows NT to Windows 95. It is not completely 213compatible in the reverse direction, however. Filenames that fit in 214the 8.3 namespace and are written on Windows NT to be lowercase will 215show up as uppercase on Windows 95. 216 217Note that the "start" and "size" values are actually little 218endian integer values. The descriptions of the fields in this 219structure are public knowledge and can be found elsewhere. 220 221With the extended FAT system, Microsoft has inserted extra 222directory entries for any files with extended names. (Any name which 223legally fits within the old 8.3 encoding scheme does not have extra 224entries.) I call these extra entries slots. Basically, a slot is a 225specially formatted directory entry which holds up to 13 characters of 226a file's extended name. Think of slots as additional labeling for the 227directory entry of the file to which they correspond. Microsoft 228prefers to refer to the 8.3 entry for a file as its alias and the 229extended slot directory entries as the file name. 230 231The C structure for a slot directory entry follows: 232 233 struct slot { // Up to 13 characters of a long name 234 unsigned char id; // sequence number for slot 235 unsigned char name0_4[10]; // first 5 characters in name 236 unsigned char attr; // attribute byte 237 unsigned char reserved; // always 0 238 unsigned char alias_checksum; // checksum for 8.3 alias 239 unsigned char name5_10[12]; // 6 more characters in name 240 unsigned char start[2]; // starting cluster number 241 unsigned char name11_12[4]; // last 2 characters in name 242 }; 243 244If the layout of the slots looks a little odd, it's only 245because of Microsoft's efforts to maintain compatibility with old 246software. The slots must be disguised to prevent old software from 247panicking. To this end, a number of measures are taken: 248 249 1) The attribute byte for a slot directory entry is always set 250 to 0x0f. This corresponds to an old directory entry with 251 attributes of "hidden", "system", "read-only", and "volume 252 label". Most old software will ignore any directory 253 entries with the "volume label" bit set. Real volume label 254 entries don't have the other three bits set. 255 256 2) The starting cluster is always set to 0, an impossible 257 value for a DOS file. 258 259Because the extended FAT system is backward compatible, it is 260possible for old software to modify directory entries. Measures must 261be taken to ensure the validity of slots. An extended FAT system can 262verify that a slot does in fact belong to an 8.3 directory entry by 263the following: 264 265 1) Positioning. Slots for a file always immediately proceed 266 their corresponding 8.3 directory entry. In addition, each 267 slot has an id which marks its order in the extended file 268 name. Here is a very abbreviated view of an 8.3 directory 269 entry and its corresponding long name slots for the file 270 "My Big File.Extension which is long": 271 272 <proceeding files...> 273 <slot #3, id = 0x43, characters = "h is long"> 274 <slot #2, id = 0x02, characters = "xtension whic"> 275 <slot #1, id = 0x01, characters = "My Big File.E"> 276 <directory entry, name = "MYBIGFIL.EXT"> 277 278 Note that the slots are stored from last to first. Slots 279 are numbered from 1 to N. The Nth slot is or'ed with 0x40 280 to mark it as the last one. 281 282 2) Checksum. Each slot has an "alias_checksum" value. The 283 checksum is calculated from the 8.3 name using the 284 following algorithm: 285 286 for (sum = i = 0; i < 11; i++) { 287 sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + name[i] 288 } 289 290 3) If there is free space in the final slot, a Unicode NULL (0x0000) 291 is stored after the final character. After that, all unused 292 characters in the final slot are set to Unicode 0xFFFF. 293 294Finally, note that the extended name is stored in Unicode. Each Unicode 295character takes two bytes. 296