Re: autofs: kernel-assisted automounter

H. Peter Anvin (
Mon, 7 Apr 1997 16:30:32 -0700 (PDT)

> > I have made a test release of autofs, a kernel-assisted automounter
> > for Linux. Currently it only supports YP (NIS) maps; I'm planning to
> > add support for a few more kinds of maps Really Soon Now[TM]. Expect
> > the versions to change quickly as the code stabilizes.
> >
> > The distribution is at:
> >
> >
> What is the difference between autofs and amd? Dan told me that it
> was supposed to be a fix for some brokeness in amd, but he could not
> tell me which brokeness he was talking about.

1. amd does everything in user space. Consequently, it (a) has to
simulate an NFS daemon and (b) cause two context switches even for
simple path lookups (i.e. the target is already mounted!) This is

2. amd is a big, monolithic monster, using a very odd format for maps.

3. amd is just plain broken code (we have had no end of trouble with
it here.)

4. "pwd" in an amd-mounted directory gives a pathname that may not
exist later during execution.

#1 and #4 are the reasons to bring it into the kernel. #2 and #3 are
just the need to get a clean code base.