
Amiga filesystems Overview
==========================

Not all varieties of the Amiga filesystems are supported.  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.
                Not supported.

DOS\1           The original Fast File System. Supported.

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.
                Not supported.

DOS\3           The "international" Fast File System.  Supported.

DOS\4           The original filesystem with directory cache. The directory
                cache speeds up directory accesses on floppies considerably,
                but slowes down file creation/deletion. Doesn't make much
                sense on hard disks. Not supported.

DOS\5           The Fast File System with directory cache. Not supported.

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.
  
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
                ommitted.

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.

use_mp          The uid and gid are taken from the now covered mount point
                instead of the current user or value defined.

mode=mode       Sets the mode flags to the given (octal) value, regardles
                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 schould never
                be neccessary.

bs=blksize      Sets the blocksize to blksize. Valid block sizes are 512,
                1024, 2048 and 4096. Like the root option, this should
                never be neccessary, as the affs can figure it out itself.

quiet           The file system will not return an error for disallowed
                mode changes.

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.

