Genera 8.1, NFS & my confusion

[barmar@Think.COM (Barry Margolin)]

    Date: Tue, 15 Oct 1991 16:22 EDT
    From: delaney@xn.ll.mit.edu (John R. Delaney)

    Our UNIX boxes are set up to mount file system on each other's disk in a
    most promiscous fashion. Then soft links are used to paper over the
    distinctions as to which files are actually on what machine's disks.
    Either clever or diabolical. I don't know enough about UNIX and NFS to
    be sure which.

We do very much the same thing.  We have file systems on about 20 Unix
systems, and over 300 workstations, and use automounts and symbolic
links so that almost any file system can be accessed from almost any
machine without the user having to know which machine it's on.

    With the advent of Genera 8.1, our Symbolic machines can now use NFS to
    access the UNIX machine file systems (which they used to to via TCP) and
    their file systems can be woven into our fabric of file systems. But
    wait! We have a problem. Certain pathnames no longer work. If the user
    tries to read file F from host H and the file is in a file system on one
    of H's own disks, all is well. If the file is actually on host H' in a
    filesystem H mounts, there is no problem with TCP. But using NFS, one
    gets an exception stating "No NFS mount could be made on host H ...
    Too many levels of remote in path for H:F".

That error means that you tried to descend into a directory that is
being used as an NFS mount point on H (the text of the message sux, but
it was copied from Unix).  NFS servers will not recursively invoke other
NFS servers; the client is supposed to know where the file actually
resides (the TCP-FTP server is an ordinary user process, so it can
access any file system that is mounted on the server).  Unix systems
have /etc/fstab and automount maps that provide this information; as you
correctly surmised, the namespace is used in Genera.

    I have rummaged through the relevant 8.1 manual (Bundled Products) and
    noticed something about AUTOMOUNT properties in the namespace. Is my
    only problem that I need those?

Yes, that is what you need.  Also, you may need the ECO #1 NFS patches,
which fix a problem in handling of symbolic links that jump across file
servers.

The NFS-AUTOMOUNT properties are pretty easy to use.  Just find the
command lines in the servers' /etc/rc.local files that invoke the
"automount" command (if you can't find them there, they might be in
another script -- ask the Unix system administrator where they are), and
copy the arguments to NFS-AUTOMOUNT properties.  For instance if host H
has the command:

	automount /net -net

then you put the following in H's namespace entry:

	NFS-AUTOMOUNT /net -net

                                                barmar