view Documentation/filesystems/affs.txt @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
line source
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.
9 Supported read/write.
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.
16 Supported read/write.
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
31 much here, either.
33 The muFS (multi user File System) equivalents of the above file systems
34 are supported, too.
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
50 will map to 600.
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.
56 root=block Sets the block number of the root block. This should never
57 be necessary.
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.
63 quiet The file system will not return an error for disallowed
64 mode changes.
66 verbose The volume name, file system type and block size will
67 be written to the syslog when the filesystem is mounted.
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.
74 prefix=path Path will be prefixed to every absolute path name of
75 symbolic links on an AFFS partition. Default = "/".
76 (See below.)
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.)
83 Handling of the Users/Groups and protection flags
84 =================================================
86 Amiga -> Linux:
88 The Amiga protection flags RWEDRWEDHSPARWED are handled as follows:
90 - R maps to r for user, group and others. On directories, R implies x.
92 - If both W and D are allowed, w will be set.
94 - E maps to x.
96 - H and P are always retained and ignored under Linux.
98 - A is always reset when a file is written to.
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).
106 Linux -> Amiga:
108 The Linux rwxrwxrwx file mode is handled as follows:
110 - r permission will set R for user, group and others.
112 - w permission will set W and D for user, group and others.
114 - x permission of the user will set E for plain files.
116 - All other flags (suid, sgid, ...) are ignored and will
117 not be retained.
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.
122 Symbolic links
123 ==============
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.
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".
144 Examples
145 ========
147 Command line:
148 mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,verbose
149 mount /dev/sda3 /Amiga -t affs
151 /etc/fstab entry:
152 /dev/sdb5 /amiga/Workbench affs noauto,user,exec,verbose 0 0
155 ==============
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!
167 If the damage is already done, the following should fix the RDB
168 (where <disk> is the device name).
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>
176 Bugs, Restrictions, Caveats
177 ===========================
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.
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).
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.
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.
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.
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.
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).
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.
217 If you are interested in an Amiga Emulator for Linux, look at
219 http://www.freiburg.linux.de/~uae/