Based on kernel version 3.9. Page generated on 2013-05-02 23:06 EST.
1 Overview of Amiga Filesystems 2 ============================= 3 4 Not all varieties of the Amiga filesystems are supported for reading and 5 writing. The Amiga currently knows six different filesystems: 6 7 DOS\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 11 DOS\1 The original Fast File System. Supported read/write. 12 13 DOS\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 18 DOS\3 The "international" Fast File System. Supported read/write. 19 20 DOS\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 25 DOS\5 The Fast File System with directory cache. Supported read only. 26 27 All of the above filesystems allow block sizes from 512 to 32K bytes. 28 Supported block sizes are: 512, 1024, 2048 and 4096 bytes. Larger blocks 29 speed up almost everything at the expense of wasted disk space. The speed 30 gain above 4K seems not really worth the price, so you don't lose too 31 much here, either. 32 33 The muFS (multi user File System) equivalents of the above file systems 34 are supported, too. 35 36 Mount options for the AFFS 37 ========================== 38 39 protect If this option is set, the protection bits cannot be altered. 40 41 setuid[=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 44 setgid[=gid] Same as above, but for gid. 45 46 mode=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 52 reserved=num Sets the number of reserved blocks at the start of the 53 partition to num. You should never need this option. 54 Default is 2. 55 56 root=block Sets the block number of the root block. This should never 57 be necessary. 58 59 bs=blksize Sets the blocksize to blksize. Valid block sizes are 512, 60 1024, 2048 and 4096. Like the root option, this should 61 never be necessary, as the affs can figure it out itself. 62 63 quiet The file system will not return an error for disallowed 64 mode changes. 65 66 verbose The volume name, file system type and block size will 67 be written to the syslog when the filesystem is mounted. 68 69 mufs The filesystem is really a muFS, also it doesn't 70 identify itself as one. This option is necessary if 71 the filesystem wasn't formatted as muFS, but is used 72 as one. 73 74 prefix=path Path will be prefixed to every absolute path name of 75 symbolic links on an AFFS partition. Default = "/". 76 (See below.) 77 78 volume=name When symbolic links with an absolute path are created 79 on an AFFS partition, name will be prepended as the 80 volume name. Default = "" (empty string). 81 (See below.) 82 83 Handling of the Users/Groups and protection flags 84 ================================================= 85 86 Amiga -> Linux: 87 88 The Amiga protection flags RWEDRWEDHSPARWED are handled as follows: 89 90 - R maps to r for user, group and others. On directories, R implies x. 91 92 - If both W and D are allowed, w will be set. 93 94 - E maps to x. 95 96 - H and P are always retained and ignored under Linux. 97 98 - A is always reset when a file is written to. 99 100 User id and group id will be used unless set[gu]id are given as mount 101 options. Since most of the Amiga file systems are single user systems 102 they will be owned by root. The root directory (the mount point) of the 103 Amiga filesystem will be owned by the user who actually mounts the 104 filesystem (the root directory doesn't have uid/gid fields). 105 106 Linux -> Amiga: 107 108 The Linux rwxrwxrwx file mode is handled as follows: 109 110 - r permission will set R for user, group and others. 111 112 - w permission will set W and D for user, group and others. 113 114 - x permission of the user will set E for plain files. 115 116 - All other flags (suid, sgid, ...) are ignored and will 117 not be retained. 118 119 Newly created files and directories will get the user and group ID 120 of the current user and a mode according to the umask. 121 122 Symbolic links 123 ============== 124 125 Although the Amiga and Linux file systems resemble each other, there 126 are some, not always subtle, differences. One of them becomes apparent 127 with symbolic links. While Linux has a file system with exactly one 128 root directory, the Amiga has a separate root directory for each 129 file system (for example, partition, floppy disk, ...). With the Amiga, 130 these entities are called "volumes". They have symbolic names which 131 can be used to access them. Thus, symbolic links can point to a 132 different volume. AFFS turns the volume name into a directory name 133 and prepends the prefix path (see prefix option) to it. 134 135 Example: 136 You mount all your Amiga partitions under /amiga/<volume> (where 137 <volume> is the name of the volume), and you give the option 138 "prefix=/amiga/" when mounting all your AFFS partitions. (They 139 might be "User", "WB" and "Graphics", the mount points /amiga/User, 140 /amiga/WB and /amiga/Graphics). A symbolic link referring to 141 "User:sc/include/dos/dos.h" will be followed to 142 "/amiga/User/sc/include/dos/dos.h". 143 144 Examples 145 ======== 146 147 Command line: 148 mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,verbose 149 mount /dev/sda3 /Amiga -t affs 150 151 /etc/fstab entry: 152 /dev/sdb5 /amiga/Workbench affs noauto,user,exec,verbose 0 0 153 154 IMPORTANT NOTE 155 ============== 156 157 If you boot Windows 95 (don't know about 3.x, 98 and NT) while you 158 have an Amiga harddisk connected to your PC, it will overwrite 159 the bytes 0x00dc..0x00df of block 0 with garbage, thus invalidating 160 the Rigid Disk Block. Sheer luck has it that this is an unused 161 area of the RDB, so only the checksum doesn't match anymore. 162 Linux will ignore this garbage and recognize the RDB anyway, but 163 before you connect that drive to your Amiga again, you must 164 restore or repair your RDB. So please do make a backup copy of it 165 before booting Windows! 166 167 If the damage is already done, the following should fix the RDB 168 (where <disk> is the device name). 169 DO AT YOUR OWN RISK: 170 171 dd if=/dev/<disk> of=rdb.tmp count=1 172 cp rdb.tmp rdb.fixed 173 dd if=/dev/zero of=rdb.fixed bs=1 seek=220 count=4 174 dd if=rdb.fixed of=/dev/<disk> 175 176 Bugs, Restrictions, Caveats 177 =========================== 178 179 Quite a few things may not work as advertised. Not everything is 180 tested, though several hundred MB have been read and written using 181 this fs. For a most up-to-date list of bugs please consult 182 fs/affs/Changes. 183 184 Filenames are truncated to 30 characters without warning (this 185 can be changed by setting the compile-time option AFFS_NO_TRUNCATE 186 in include/linux/amigaffs.h). 187 188 Case is ignored by the affs in filename matching, but Linux shells 189 do care about the case. Example (with /wb being an affs mounted fs): 190 rm /wb/WRONGCASE 191 will remove /mnt/wrongcase, but 192 rm /wb/WR* 193 will not since the names are matched by the shell. 194 195 The block allocation is designed for hard disk partitions. If more 196 than 1 process writes to a (small) diskette, the blocks are allocated 197 in an ugly way (but the real AFFS doesn't do much better). This 198 is also true when space gets tight. 199 200 You cannot execute programs on an OFS (Old File System), since the 201 program files cannot be memory mapped due to the 488 byte blocks. 202 For the same reason you cannot mount an image on such a filesystem 203 via the loopback device. 204 205 The bitmap valid flag in the root block may not be accurate when the 206 system crashes while an affs partition is mounted. There's currently 207 no way to fix a garbled filesystem without an Amiga (disk validator) 208 or manually (who would do this?). Maybe later. 209 210 If you mount affs partitions on system startup, you may want to tell 211 fsck that the fs should not be checked (place a '0' in the sixth field 212 of /etc/fstab). 213 214 It's not possible to read floppy disks with a normal PC or workstation 215 due to an incompatibility with the Amiga floppy controller. 216 217 If you are interested in an Amiga Emulator for Linux, look at 218 219 http://web.archive.org/web/*/http://www.freiburg.linux.de/~uae/