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Linus Torvalds1da177e2005-04-16 15:20:36 -07001Overview 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
Fabian Frederick8ca57722014-04-07 15:39:01 -070052nofilenametruncate
53 The file system will return an error when filename exceeds
54 standard maximum filename length (30 characters).
55
Linus Torvalds1da177e2005-04-16 15:20:36 -070056reserved=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
Max Staudte942ed82020-08-27 17:49:00 +020096 - W maps to w.
Linus Torvalds1da177e2005-04-16 15:20:36 -070097
98 - E maps to x.
99
Max Staudte942ed82020-08-27 17:49:00 +0200100 - D is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101
Max Staudte942ed82020-08-27 17:49:00 +0200102 - H, S and P are always retained and ignored under Linux.
103
104 - A is cleared when a file is written to.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105
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
Max Staudte942ed82020-08-27 17:49:00 +0200116 - r permission will allow R for user, group and others.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117
Max Staudte942ed82020-08-27 17:49:00 +0200118 - w permission will allow W for user, group and others.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
Max Staudte942ed82020-08-27 17:49:00 +0200120 - x permission of the user will allow E for plain files.
121
122 - D will be allowed for user, group and others.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123
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
Fabian Frederick8ca57722014-04-07 15:39:01 -0700192By default, filenames are truncated to 30 characters without warning.
193'nofilenametruncate' mount option can change that behavior.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194
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
Justin P. Mattock0ea6e612010-07-23 20:51:24 -0700226http://web.archive.org/web/*/http://www.freiburg.linux.de/~uae/