Based on kernel version 4.0. Page generated on 2015-04-14 21:24 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 nofilenametruncate 53 The file system will return an error when filename exceeds 54 standard maximum filename length (30 characters). 55 56 reserved=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 60 root=block Sets the block number of the root block. This should never 61 be necessary. 62 63 bs=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 67 quiet The file system will not return an error for disallowed 68 mode changes. 69 70 verbose The volume name, file system type and block size will 71 be written to the syslog when the filesystem is mounted. 72 73 mufs 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 78 prefix=path Path will be prefixed to every absolute path name of 79 symbolic links on an AFFS partition. Default = "/". 80 (See below.) 81 82 volume=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 87 Handling of the Users/Groups and protection flags 88 ================================================= 89 90 Amiga -> Linux: 91 92 The 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 - If both W and D are allowed, w will be set. 97 98 - E maps to x. 99 100 - H and P are always retained and ignored under Linux. 101 102 - A is always reset when a file is written to. 103 104 User id and group id will be used unless set[gu]id are given as mount 105 options. Since most of the Amiga file systems are single user systems 106 they will be owned by root. The root directory (the mount point) of the 107 Amiga filesystem will be owned by the user who actually mounts the 108 filesystem (the root directory doesn't have uid/gid fields). 109 110 Linux -> Amiga: 111 112 The Linux rwxrwxrwx file mode is handled as follows: 113 114 - r permission will set R for user, group and others. 115 116 - w permission will set W and D for user, group and others. 117 118 - x permission of the user will set E for plain files. 119 120 - All other flags (suid, sgid, ...) are ignored and will 121 not be retained. 122 123 Newly created files and directories will get the user and group ID 124 of the current user and a mode according to the umask. 125 126 Symbolic links 127 ============== 128 129 Although the Amiga and Linux file systems resemble each other, there 130 are some, not always subtle, differences. One of them becomes apparent 131 with symbolic links. While Linux has a file system with exactly one 132 root directory, the Amiga has a separate root directory for each 133 file system (for example, partition, floppy disk, ...). With the Amiga, 134 these entities are called "volumes". They have symbolic names which 135 can be used to access them. Thus, symbolic links can point to a 136 different volume. AFFS turns the volume name into a directory name 137 and prepends the prefix path (see prefix option) to it. 138 139 Example: 140 You mount all your Amiga partitions under /amiga/<volume> (where 141 <volume> is the name of the volume), and you give the option 142 "prefix=/amiga/" when mounting all your AFFS partitions. (They 143 might be "User", "WB" and "Graphics", the mount points /amiga/User, 144 /amiga/WB and /amiga/Graphics). A symbolic link referring to 145 "User:sc/include/dos/dos.h" will be followed to 146 "/amiga/User/sc/include/dos/dos.h". 147 148 Examples 149 ======== 150 151 Command line: 152 mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,verbose 153 mount /dev/sda3 /Amiga -t affs 154 155 /etc/fstab entry: 156 /dev/sdb5 /amiga/Workbench affs noauto,user,exec,verbose 0 0 157 158 IMPORTANT NOTE 159 ============== 160 161 If you boot Windows 95 (don't know about 3.x, 98 and NT) while you 162 have an Amiga harddisk connected to your PC, it will overwrite 163 the bytes 0x00dc..0x00df of block 0 with garbage, thus invalidating 164 the Rigid Disk Block. Sheer luck has it that this is an unused 165 area of the RDB, so only the checksum doesn't match anymore. 166 Linux will ignore this garbage and recognize the RDB anyway, but 167 before you connect that drive to your Amiga again, you must 168 restore or repair your RDB. So please do make a backup copy of it 169 before booting Windows! 170 171 If the damage is already done, the following should fix the RDB 172 (where <disk> is the device name). 173 DO AT YOUR OWN RISK: 174 175 dd if=/dev/<disk> of=rdb.tmp count=1 176 cp rdb.tmp rdb.fixed 177 dd if=/dev/zero of=rdb.fixed bs=1 seek=220 count=4 178 dd if=rdb.fixed of=/dev/<disk> 179 180 Bugs, Restrictions, Caveats 181 =========================== 182 183 Quite a few things may not work as advertised. Not everything is 184 tested, though several hundred MB have been read and written using 185 this fs. For a most up-to-date list of bugs please consult 186 fs/affs/Changes. 187 188 By default, filenames are truncated to 30 characters without warning. 189 'nofilenametruncate' mount option can change that behavior. 190 191 Case is ignored by the affs in filename matching, but Linux shells 192 do care about the case. Example (with /wb being an affs mounted fs): 193 rm /wb/WRONGCASE 194 will remove /mnt/wrongcase, but 195 rm /wb/WR* 196 will not since the names are matched by the shell. 197 198 The block allocation is designed for hard disk partitions. If more 199 than 1 process writes to a (small) diskette, the blocks are allocated 200 in an ugly way (but the real AFFS doesn't do much better). This 201 is also true when space gets tight. 202 203 You cannot execute programs on an OFS (Old File System), since the 204 program files cannot be memory mapped due to the 488 byte blocks. 205 For the same reason you cannot mount an image on such a filesystem 206 via the loopback device. 207 208 The bitmap valid flag in the root block may not be accurate when the 209 system crashes while an affs partition is mounted. There's currently 210 no way to fix a garbled filesystem without an Amiga (disk validator) 211 or manually (who would do this?). Maybe later. 212 213 If you mount affs partitions on system startup, you may want to tell 214 fsck that the fs should not be checked (place a '0' in the sixth field 215 of /etc/fstab). 216 217 It's not possible to read floppy disks with a normal PC or workstation 218 due to an incompatibility with the Amiga floppy controller. 219 220 If you are interested in an Amiga Emulator for Linux, look at 221 222 http://web.archive.org/web/*/http://www.freiburg.linux.de/~uae/