1Overview of Amiga Filesystems 2============================= 3 4Not all varieties of the Amiga filesystems are supported for reading and 5writing. The Amiga currently knows six different filesystems: 6 7DOS\0 The old or original filesystem, not really suited for 8 hard disks and normally not used on them, either. 9 Supported read/write. 10 11DOS\1 The original Fast File System. Supported read/write. 12 13DOS\2 The old "international" filesystem. International means that 14 a bug has been fixed so that accented ("international") letters 15 in file names are case-insensitive, as they ought to be. 16 Supported read/write. 17 18DOS\3 The "international" Fast File System. Supported read/write. 19 20DOS\4 The original filesystem with directory cache. The directory 21 cache speeds up directory accesses on floppies considerably, 22 but slows down file creation/deletion. Doesn't make much 23 sense on hard disks. Supported read only. 24 25DOS\5 The Fast File System with directory cache. Supported read only. 26 27All of the above filesystems allow block sizes from 512 to 32K bytes. 28Supported block sizes are: 512, 1024, 2048 and 4096 bytes. Larger blocks 29speed up almost everything at the expense of wasted disk space. The speed 30gain above 4K seems not really worth the price, so you don't lose too 31much here, either. 32 33The muFS (multi user File System) equivalents of the above file systems 34are supported, too. 35 36Mount options for the AFFS 37========================== 38 39protect If this option is set, the protection bits cannot be altered. 40 41setuid[=uid] This sets the owner of all files and directories in the file 42 system to uid or the uid of the current user, respectively. 43 44setgid[=gid] Same as above, but for gid. 45 46mode=mode Sets the mode flags to the given (octal) value, regardless 47 of the original permissions. Directories will get an x 48 permission if the corresponding r bit is set. 49 This is useful since most of the plain AmigaOS files 50 will map to 600. 51 52nofilenametruncate 53 The file system will return an error when filename exceeds 54 standard maximum filename length (30 characters). 55 56reserved=num Sets the number of reserved blocks at the start of the 57 partition to num. You should never need this option. 58 Default is 2. 59 60root=block Sets the block number of the root block. This should never 61 be necessary. 62 63bs=blksize Sets the blocksize to blksize. Valid block sizes are 512, 64 1024, 2048 and 4096. Like the root option, this should 65 never be necessary, as the affs can figure it out itself. 66 67quiet The file system will not return an error for disallowed 68 mode changes. 69 70verbose The volume name, file system type and block size will 71 be written to the syslog when the filesystem is mounted. 72 73mufs The filesystem is really a muFS, also it doesn't 74 identify itself as one. This option is necessary if 75 the filesystem wasn't formatted as muFS, but is used 76 as one. 77 78prefix=path Path will be prefixed to every absolute path name of 79 symbolic links on an AFFS partition. Default = "/". 80 (See below.) 81 82volume=name When symbolic links with an absolute path are created 83 on an AFFS partition, name will be prepended as the 84 volume name. Default = "" (empty string). 85 (See below.) 86 87Handling of the Users/Groups and protection flags 88================================================= 89 90Amiga -> Linux: 91 92The Amiga protection flags RWEDRWEDHSPARWED are handled as follows: 93 94 - R maps to r for user, group and others. On directories, R implies x. 95 96 - W maps to w. 97 98 - E maps to x. 99 100 - D is ignored. 101 102 - H, S and P are always retained and ignored under Linux. 103 104 - A is cleared when a file is written to. 105 106User id and group id will be used unless set[gu]id are given as mount 107options. Since most of the Amiga file systems are single user systems 108they will be owned by root. The root directory (the mount point) of the 109Amiga filesystem will be owned by the user who actually mounts the 110filesystem (the root directory doesn't have uid/gid fields). 111 112Linux -> Amiga: 113 114The Linux rwxrwxrwx file mode is handled as follows: 115 116 - r permission will allow R for user, group and others. 117 118 - w permission will allow W for user, group and others. 119 120 - x permission of the user will allow E for plain files. 121 122 - D will be allowed for user, group and others. 123 124 - All other flags (suid, sgid, ...) are ignored and will 125 not be retained. 126 127Newly created files and directories will get the user and group ID 128of the current user and a mode according to the umask. 129 130Symbolic links 131============== 132 133Although the Amiga and Linux file systems resemble each other, there 134are some, not always subtle, differences. One of them becomes apparent 135with symbolic links. While Linux has a file system with exactly one 136root directory, the Amiga has a separate root directory for each 137file system (for example, partition, floppy disk, ...). With the Amiga, 138these entities are called "volumes". They have symbolic names which 139can be used to access them. Thus, symbolic links can point to a 140different volume. AFFS turns the volume name into a directory name 141and prepends the prefix path (see prefix option) to it. 142 143Example: 144You mount all your Amiga partitions under /amiga/<volume> (where 145<volume> is the name of the volume), and you give the option 146"prefix=/amiga/" when mounting all your AFFS partitions. (They 147might be "User", "WB" and "Graphics", the mount points /amiga/User, 148/amiga/WB and /amiga/Graphics). A symbolic link referring to 149"User:sc/include/dos/dos.h" will be followed to 150"/amiga/User/sc/include/dos/dos.h". 151 152Examples 153======== 154 155Command line: 156 mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,verbose 157 mount /dev/sda3 /Amiga -t affs 158 159/etc/fstab entry: 160 /dev/sdb5 /amiga/Workbench affs noauto,user,exec,verbose 0 0 161 162IMPORTANT NOTE 163============== 164 165If you boot Windows 95 (don't know about 3.x, 98 and NT) while you 166have an Amiga harddisk connected to your PC, it will overwrite 167the bytes 0x00dc..0x00df of block 0 with garbage, thus invalidating 168the Rigid Disk Block. Sheer luck has it that this is an unused 169area of the RDB, so only the checksum doesn't match anymore. 170Linux will ignore this garbage and recognize the RDB anyway, but 171before you connect that drive to your Amiga again, you must 172restore or repair your RDB. So please do make a backup copy of it 173before booting Windows! 174 175If the damage is already done, the following should fix the RDB 176(where <disk> is the device name). 177DO AT YOUR OWN RISK: 178 179 dd if=/dev/<disk> of=rdb.tmp count=1 180 cp rdb.tmp rdb.fixed 181 dd if=/dev/zero of=rdb.fixed bs=1 seek=220 count=4 182 dd if=rdb.fixed of=/dev/<disk> 183 184Bugs, Restrictions, Caveats 185=========================== 186 187Quite a few things may not work as advertised. Not everything is 188tested, though several hundred MB have been read and written using 189this fs. For a most up-to-date list of bugs please consult 190fs/affs/Changes. 191 192By default, filenames are truncated to 30 characters without warning. 193'nofilenametruncate' mount option can change that behavior. 194 195Case is ignored by the affs in filename matching, but Linux shells 196do care about the case. Example (with /wb being an affs mounted fs): 197 rm /wb/WRONGCASE 198will remove /mnt/wrongcase, but 199 rm /wb/WR* 200will not since the names are matched by the shell. 201 202The block allocation is designed for hard disk partitions. If more 203than 1 process writes to a (small) diskette, the blocks are allocated 204in an ugly way (but the real AFFS doesn't do much better). This 205is also true when space gets tight. 206 207You cannot execute programs on an OFS (Old File System), since the 208program files cannot be memory mapped due to the 488 byte blocks. 209For the same reason you cannot mount an image on such a filesystem 210via the loopback device. 211 212The bitmap valid flag in the root block may not be accurate when the 213system crashes while an affs partition is mounted. There's currently 214no way to fix a garbled filesystem without an Amiga (disk validator) 215or manually (who would do this?). Maybe later. 216 217If you mount affs partitions on system startup, you may want to tell 218fsck that the fs should not be checked (place a '0' in the sixth field 219of /etc/fstab). 220 221It's not possible to read floppy disks with a normal PC or workstation 222due to an incompatibility with the Amiga floppy controller. 223 224If you are interested in an Amiga Emulator for Linux, look at 225 226http://web.archive.org/web/*/http://www.freiburg.linux.de/~uae/ 227