the null mount, we currently create a temporary mfs on /tmp, copy
/etc to /tmp, then mount /etc as mfs and copy everything back from
/tmp, then delete the /tmp mfs.
The patch eliminates the temporary /tmp mfs and the subsequent
copying and simply populates the /etc mfs by copying from
/conf/default/etc. This requires that /conf/default/etc contain a
complete copy of all the /etc stuff instead of just overrides. I
don't think that is too much of an extra step in setting up a
diskless environment.
* Provide the ability to make /tmp a memory filesystem independent
of /var. This removes the requirement that /tmp be a symlink to
/var/tmp and this makes the diskless code work with the default
filesystem layout. If a seperate /tmp memory filesystem is
created, the 'tmpsize' environment variable is used to determine
its size (default to 10 Meg).
* Reduce diffs between the -current and -stable versions of these
files to a bare minimum. Only the definition of the shell
function 'mount_md' is different.
Not Objected to by: -arch@, -small@
MFC after: 2 days
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