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Based on kernel version 3.13. Page generated on 2014-01-20 22:02 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/
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