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 140discard -- If set, issues discard/TRIM commands to the block 141 device when blocks are freed. This is useful for SSD devices 142 and sparse/thinly-provisoned LUNs. 143 144nfs -- This option maintains an index (cache) of directory 145 inodes by i_logstart which is used by the nfs-related code to 146 improve look-ups. 147 148 Enable this only if you want to export the FAT filesystem 149 over NFS 150 151<bool>: 0,1,yes,no,true,false 152 153TODO 154---------------------------------------------------------------------- 155* Need to get rid of the raw scanning stuff. Instead, always use 156 a get next directory entry approach. The only thing left that uses 157 raw scanning is the directory renaming code. 158 159 160POSSIBLE PROBLEMS 161---------------------------------------------------------------------- 162* vfat_valid_longname does not properly checked reserved names. 163* When a volume name is the same as a directory name in the root 164 directory of the filesystem, the directory name sometimes shows 165 up as an empty file. 166* autoconv option does not work correctly. 167 168BUG REPORTS 169---------------------------------------------------------------------- 170If you have trouble with the VFAT filesystem, mail bug reports to 171chaffee@bmrc.cs.berkeley.edu. Please specify the filename 172and the operation that gave you trouble. 173 174TEST SUITE 175---------------------------------------------------------------------- 176If you plan to make any modifications to the vfat filesystem, please 177get the test suite that comes with the vfat distribution at 178 179 http://web.archive.org/web/*/http://bmrc.berkeley.edu/ 180 people/chaffee/vfat.html 181 182This tests quite a few parts of the vfat filesystem and additional 183tests for new features or untested features would be appreciated. 184 185NOTES ON THE STRUCTURE OF THE VFAT FILESYSTEM 186---------------------------------------------------------------------- 187(This documentation was provided by Galen C. Hunt <gchunt@cs.rochester.edu> 188 and lightly annotated by Gordon Chaffee). 189 190This document presents a very rough, technical overview of my 191knowledge of the extended FAT file system used in Windows NT 3.5 and 192Windows 95. I don't guarantee that any of the following is correct, 193but it appears to be so. 194 195The extended FAT file system is almost identical to the FAT 196file system used in DOS versions up to and including 6.223410239847 197:-). The significant change has been the addition of long file names. 198These names support up to 255 characters including spaces and lower 199case characters as opposed to the traditional 8.3 short names. 200 201Here is the description of the traditional FAT entry in the current 202Windows 95 filesystem: 203 204 struct directory { // Short 8.3 names 205 unsigned char name[8]; // file name 206 unsigned char ext[3]; // file extension 207 unsigned char attr; // attribute byte 208 unsigned char lcase; // Case for base and extension 209 unsigned char ctime_ms; // Creation time, milliseconds 210 unsigned char ctime[2]; // Creation time 211 unsigned char cdate[2]; // Creation date 212 unsigned char adate[2]; // Last access date 213 unsigned char reserved[2]; // reserved values (ignored) 214 unsigned char time[2]; // time stamp 215 unsigned char date[2]; // date stamp 216 unsigned char start[2]; // starting cluster number 217 unsigned char size[4]; // size of the file 218 }; 219 220The lcase field specifies if the base and/or the extension of an 8.3 221name should be capitalized. This field does not seem to be used by 222Windows 95 but it is used by Windows NT. The case of filenames is not 223completely compatible from Windows NT to Windows 95. It is not completely 224compatible in the reverse direction, however. Filenames that fit in 225the 8.3 namespace and are written on Windows NT to be lowercase will 226show up as uppercase on Windows 95. 227 228Note that the "start" and "size" values are actually little 229endian integer values. The descriptions of the fields in this 230structure are public knowledge and can be found elsewhere. 231 232With the extended FAT system, Microsoft has inserted extra 233directory entries for any files with extended names. (Any name which 234legally fits within the old 8.3 encoding scheme does not have extra 235entries.) I call these extra entries slots. Basically, a slot is a 236specially formatted directory entry which holds up to 13 characters of 237a file's extended name. Think of slots as additional labeling for the 238directory entry of the file to which they correspond. Microsoft 239prefers to refer to the 8.3 entry for a file as its alias and the 240extended slot directory entries as the file name. 241 242The C structure for a slot directory entry follows: 243 244 struct slot { // Up to 13 characters of a long name 245 unsigned char id; // sequence number for slot 246 unsigned char name0_4[10]; // first 5 characters in name 247 unsigned char attr; // attribute byte 248 unsigned char reserved; // always 0 249 unsigned char alias_checksum; // checksum for 8.3 alias 250 unsigned char name5_10[12]; // 6 more characters in name 251 unsigned char start[2]; // starting cluster number 252 unsigned char name11_12[4]; // last 2 characters in name 253 }; 254 255If the layout of the slots looks a little odd, it's only 256because of Microsoft's efforts to maintain compatibility with old 257software. The slots must be disguised to prevent old software from 258panicking. To this end, a number of measures are taken: 259 260 1) The attribute byte for a slot directory entry is always set 261 to 0x0f. This corresponds to an old directory entry with 262 attributes of "hidden", "system", "read-only", and "volume 263 label". Most old software will ignore any directory 264 entries with the "volume label" bit set. Real volume label 265 entries don't have the other three bits set. 266 267 2) The starting cluster is always set to 0, an impossible 268 value for a DOS file. 269 270Because the extended FAT system is backward compatible, it is 271possible for old software to modify directory entries. Measures must 272be taken to ensure the validity of slots. An extended FAT system can 273verify that a slot does in fact belong to an 8.3 directory entry by 274the following: 275 276 1) Positioning. Slots for a file always immediately proceed 277 their corresponding 8.3 directory entry. In addition, each 278 slot has an id which marks its order in the extended file 279 name. Here is a very abbreviated view of an 8.3 directory 280 entry and its corresponding long name slots for the file 281 "My Big File.Extension which is long": 282 283 <proceeding files...> 284 <slot #3, id = 0x43, characters = "h is long"> 285 <slot #2, id = 0x02, characters = "xtension whic"> 286 <slot #1, id = 0x01, characters = "My Big File.E"> 287 <directory entry, name = "MYBIGFIL.EXT"> 288 289 Note that the slots are stored from last to first. Slots 290 are numbered from 1 to N. The Nth slot is or'ed with 0x40 291 to mark it as the last one. 292 293 2) Checksum. Each slot has an "alias_checksum" value. The 294 checksum is calculated from the 8.3 name using the 295 following algorithm: 296 297 for (sum = i = 0; i < 11; i++) { 298 sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + name[i] 299 } 300 301 3) If there is free space in the final slot, a Unicode NULL (0x0000) 302 is stored after the final character. After that, all unused 303 characters in the final slot are set to Unicode 0xFFFF. 304 305Finally, note that the extended name is stored in Unicode. Each Unicode 306character takes two bytes. 307