1 Overview of Amiga Filesystems
2 =============================
4 Not all varieties of the Amiga filesystems are supported for reading and
5 writing. The Amiga currently knows six different filesystems:
7 DOS\0 The old or original filesystem, not really suited for
8 hard disks and normally not used on them, either.
11 DOS\1 The original Fast File System. Supported read/write.
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.
18 DOS\3 The "international" Fast File System. Supported read/write.
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.
25 DOS\5 The Fast File System with directory cache. Supported read only.
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
33 The muFS (multi user File System) equivalents of the above file systems
36 Mount options for the AFFS
37 ==========================
39 protect If this option is set, the protection bits cannot be altered.
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.
44 setgid[=gid] Same as above, but for gid.
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
53 The file system will return an error when filename exceeds
54 standard maximum filename length (30 characters).
56 reserved=num Sets the number of reserved blocks at the start of the
57 partition to num. You should never need this option.
60 root=block Sets the block number of the root block. This should never
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.
67 quiet The file system will not return an error for disallowed
70 verbose The volume name, file system type and block size will
71 be written to the syslog when the filesystem is mounted.
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
78 prefix=path Path will be prefixed to every absolute path name of
79 symbolic links on an AFFS partition. Default = "/".
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).
87 Handling of the Users/Groups and protection flags
88 =================================================
92 The Amiga protection flags RWEDRWEDHSPARWED are handled as follows:
94 - R maps to r for user, group and others. On directories, R implies x.
102 - H, S and P are always retained and ignored under Linux.
104 - A is cleared when a file is written to.
106 User id and group id will be used unless set[gu]id are given as mount
107 options. Since most of the Amiga file systems are single user systems
108 they will be owned by root. The root directory (the mount point) of the
109 Amiga filesystem will be owned by the user who actually mounts the
110 filesystem (the root directory doesn't have uid/gid fields).
114 The Linux rwxrwxrwx file mode is handled as follows:
116 - r permission will allow R for user, group and others.
118 - w permission will allow W for user, group and others.
120 - x permission of the user will allow E for plain files.
122 - D will be allowed for user, group and others.
124 - All other flags (suid, sgid, ...) are ignored and will
127 Newly created files and directories will get the user and group ID
128 of the current user and a mode according to the umask.
133 Although the Amiga and Linux file systems resemble each other, there
134 are some, not always subtle, differences. One of them becomes apparent
135 with symbolic links. While Linux has a file system with exactly one
136 root directory, the Amiga has a separate root directory for each
137 file system (for example, partition, floppy disk, ...). With the Amiga,
138 these entities are called "volumes". They have symbolic names which
139 can be used to access them. Thus, symbolic links can point to a
140 different volume. AFFS turns the volume name into a directory name
141 and prepends the prefix path (see prefix option) to it.
144 You 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
147 might 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".
156 mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,verbose
157 mount /dev/sda3 /Amiga -t affs
160 /dev/sdb5 /amiga/Workbench affs noauto,user,exec,verbose 0 0
165 If you boot Windows 95 (don't know about 3.x, 98 and NT) while you
166 have an Amiga harddisk connected to your PC, it will overwrite
167 the bytes 0x00dc..0x00df of block 0 with garbage, thus invalidating
168 the Rigid Disk Block. Sheer luck has it that this is an unused
169 area of the RDB, so only the checksum doesn't match anymore.
170 Linux will ignore this garbage and recognize the RDB anyway, but
171 before you connect that drive to your Amiga again, you must
172 restore or repair your RDB. So please do make a backup copy of it
173 before booting Windows!
175 If the damage is already done, the following should fix the RDB
176 (where <disk> is the device name).
179 dd if=/dev/<disk> of=rdb.tmp count=1
181 dd if=/dev/zero of=rdb.fixed bs=1 seek=220 count=4
182 dd if=rdb.fixed of=/dev/<disk>
184 Bugs, Restrictions, Caveats
185 ===========================
187 Quite a few things may not work as advertised. Not everything is
188 tested, though several hundred MB have been read and written using
189 this fs. For a most up-to-date list of bugs please consult
192 By default, filenames are truncated to 30 characters without warning.
193 'nofilenametruncate' mount option can change that behavior.
195 Case is ignored by the affs in filename matching, but Linux shells
196 do care about the case. Example (with /wb being an affs mounted fs):
198 will remove /mnt/wrongcase, but
200 will not since the names are matched by the shell.
202 The block allocation is designed for hard disk partitions. If more
203 than 1 process writes to a (small) diskette, the blocks are allocated
204 in an ugly way (but the real AFFS doesn't do much better). This
205 is also true when space gets tight.
207 You cannot execute programs on an OFS (Old File System), since the
208 program files cannot be memory mapped due to the 488 byte blocks.
209 For the same reason you cannot mount an image on such a filesystem
210 via the loopback device.
212 The bitmap valid flag in the root block may not be accurate when the
213 system crashes while an affs partition is mounted. There's currently
214 no way to fix a garbled filesystem without an Amiga (disk validator)
215 or manually (who would do this?). Maybe later.
217 If you mount affs partitions on system startup, you may want to tell
218 fsck that the fs should not be checked (place a '0' in the sixth field
221 It's not possible to read floppy disks with a normal PC or workstation
222 due to an incompatibility with the Amiga floppy controller.
224 If you are interested in an Amiga Emulator for Linux, look at
226 http://web.archive.org/web/*/http://www.freiburg.linux.de/~uae/