Subject: Re: NetBSD/Mac68k and X11 Windows
To: Dave Slotter <email@example.com>
From: Chris G. Demetriou <firstname.lastname@example.org>
Date: 09/15/1994 19:12:05
> It's interesting to see that you can do this, but can you do the reverse,
> i.e. mount the BSD file system (read only or read/write) on A/UX?
No, you shouldn't be able to.
There are three formats of Berkeley Fast File System, and the
differences between them are mentioned in the 'fsck' man page:
-c Convert the filesystem to the specified level. Note that the
level of a filesystem can only be raised. There are currently
three levels defined:
0 The filesystem is in the old (static table) format.
1 The filesystem is in the new (dynamic table) format.
2 The filesystem supports 32-bit uid's and gid's, short
symbolic links are stored in the inode, and directories
have an added field showing the file type.
A/UX, and many other commercial SysV-ish UN*Xes (e.g. AMIX, for the
amiga, etc.) use level 0 format file systems. Their FFS code was
derived from the 4.2BSD FFS code, which was "level 0".
NetBSD used to use level 1 format file systems, as that was the format
supported by the Net/2 release from Berkeley.
The 4.4Lite distribution made the level 2 format the default, and
that's what NetBSD now uses. The 4.4Lite 'newfs' also allows creation
of level 1 format file systems, for systems whose ROMs and standard
boot blocks (e.g. Sun SPARCs, i think) don't support booting off of
level 2 format file systems, and for which new boot blocks have not
yet been written.
Systems supporting a certain level can't use file systems of a
higher level, so A/UX and AMIX can't use either of the NetBSD file
Systems supporting the level 1 or level 2 formats can safely read --
but not write -- level 0 format file systems, so NetBSD can mount A/UX
or AMIX FFS (but not SysV) file systems read-only.
Systems supporting level 2 file systems can safely read _and_ write
level 1 format file systems.