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diff --git a/Documentation/filesystems/affs.txt b/Documentation/filesystems/affs.txt new file mode 100644 index 000000000..c5d329ec6 --- /dev/null +++ b/Documentation/filesystems/affs.txt @@ -0,0 +1,188 @@ +Amiga filesystems Overview +========================== + +Not all varieties of the Amiga filesystems are supported for reading and +writing. The Amiga currently knows 6 different filesystems: + +DOS\0 The old or original filesystem, not really suited for + hard disks and normally not used on them, either. + Supported read/write. + +DOS\1 The original Fast File System. Supported read/write. + +DOS\2 The old "international" filesystem. International means that + a bug has been fixed so that accented ("international") letters + in file names are case-insensitive, as they ought to be. + Supported read/write. + +DOS\3 The "international" Fast File System. Supported read/write. + +DOS\4 The original filesystem with directory cache. The directory + cache speeds up directory accesses on floppies considerably, + but slows down file creation/deletion. Doesn't make much + sense on hard disks. Supported read only. + +DOS\5 The Fast File System with directory cache. Supported read only. + +All of the above filesystems allow block sizes from 512 to 32K bytes. +Supported block sizes are: 512, 1024, 2048 and 4096 bytes. Larger blocks +speed up almost everything with the expense of wasted disk space. The speed +gain above 4K seems not really worth the price, so you don't lose too +much here, either. + +The muFS (multi user File System) equivalents of the above file systems +are supported, too. + +Mount options for the AFFS +========================== + +protect If this option is set, the protection bits cannot be altered. + +uid[=uid] This sets the uid of the root directory (i. e. the mount point + to uid or to the uid of the current user, if the =uid is + omitted. + +gid[=gid] Same as above, but for gid. + +setuid[=uid] This sets the owner of all files and directories in the file + system to uid or the uid of the current user, respectively. + +setgid[=gid] Same as above, but for gid. + +mode=mode Sets the mode flags to the given (octal) value, regardless + of the original permissions. Directories will get an x + permission, if the corresponding r bit is set. + This is useful since most of the plain AmigaOS files + will map to 600. + +reserved=num Sets the number of reserved blocks at the start of the + partition to num. Default is 2. + +root=block Sets the block number of the root block. This should never + be necessary. + +bs=blksize Sets the blocksize to blksize. Valid block sizes are 512, + 1024, 2048 and 4096. Like the root option, this should + never be necessary, as the affs can figure it out itself. + +quiet The file system will not return an error for disallowed + mode changes. + +verbose The volume name, file system type and block size will + be written to the syslog. + +prefix=path Path will be prefixed to every absolute path name of + symbolic links on an AFFS partition. Default = / + +volume=name When symbolic links with an absolute path are created + on an AFFS partition, volume will be prepended as the + volume name. Default = "" (empty string). + +Handling of the Users/Groups and protection flags +================================================= + +Amiga -> Linux: + +The Amiga protection flags RWEDRWEDHSPARWED are handled as follows: + + - R maps to r for user, group and others. On directories, R implies x. + + - If both W and D are allowed, w will be set. + + - If both R and S are set, x will be set. + + - H, P and E are always retained and ignored under Linux. + + - A is always reset when written. + +User id and group id will be used unless set[gu]id are given as mount +options. Since most of the Amiga file systems are single user systems +they will be owned by root. + +Linux -> Amiga: + +The Linux rwxrwxrwx file mode is handled as follows: + + - r permission will set R for user, group and others. + + - w permission will set W and D for user, group and others. + + - x permission of the user will set S for plain files. + + - All other flags (suid, sgid, ...) are ignored and will + not be retained. + +Newly created files and directories will get the user and group id +of the current user and a mode according to the umask. + +Symbolic links +============== + +Although the Amiga and Linux file systems resemble each other, there +are some, not always subtle, differences. One of them becomes apparent +with symbolic links. While Linux has a file system with exactly one +root directory, the Amiga has a seperate root directory for each +file system (i. e. partition, floppy disk, ...). With the Amiga, +these entities are called "volumes". They have symbolic names which +can be used to access them. Thus, symbolic links can point to a +different volume. AFFS turns the volume name into a directory name +and prepends the prefix path (see prefix option) to it. + +Example: +You mount all your Amiga partitions under /amiga/<volume> (where +<volume> is the name of the volume), and you give the option +"prefix=/amiga/" when mounting all your AFFS partitions. (They +might be "User", "WB" and "Graphics", the mount points /amiga/User, +/amiga/WB and /amiga/Graphics). A symbolic link referring to +"User:sc/include/dos/dos.h" will be followed to +"/amiga/User/sc/include/dos/dos.h". + +Examples +======== + +Command line + mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,reserved=4 + mount /dev/sda3 /Amiga -t affs + +/etc/fstab example + /dev/sdb5 /d/f affs ro + +Bugs, Restrictions, Caveats +=========================== + +Quite a few things may not work as advertised. Not everything is +tested, though several hundred MB have been read and written using +this fs. + +Filenames are truncated to 30 characters without warning. + +Currently there are no checks against invalid characters (':') +in filenames. + +Case is ignored by the affs in filename matching, but Linux shells +do care about the case. Example (with /mnt being an affs mounted fs): + rm /mnt/WRONGCASE +will remove /mnt/wrongcase, but + rm /mnt/WR* +will not since the names are matched by the shell. + +The block allocation is designed for hard disk partitions. If more +than 1 process writes to a (small) diskette, the blocks are allocated +in an ugly way (but the real AFFS doesn't do much better). This +is also true when space gets tight. + +The bitmap valid flag in the root block may not be accurate when the +system crashes while an affs partition is mounted. There's currently +no way to fix this without an Amiga (disk validator) or manually +(who would do this?). Maybe later. + +A fsck.affs and mkfs.affs will probably be available in the future. +Until then, you should do + ln -s /bin/true /etc/fs/mkfs.affs + +It's not possible to read floppy disks with a normal PC or workstation +due to an incompatibility with the Amiga floppy controller. + +If you are interested in an Amiga Emulator for Linux, look at + +http://www-users.informatik.rwth-aachen.de/~crux/uae.html |