Apparently, backup cannot see the volutil command in its PATH.  I'm
  going to hardcode the location, since backup does not by default have
  its PATH set to /usr/sbin... etc., and try again.

[warning: talking without having read all the code]
I believe that programs like this should have fully qualified paths
compiled in using $(prefix) from configure time.  But I think debian
doesn't like this, and there is some notion of run-time moving of
trees (hence the no-rpath rule).

I suppose you could in the meantime just kludge around this with a
symlink in /usr/sbin or something.

  I'm also wondering if
  the backup user has the correct permissions to be allowed to export
  data, etc. from coda volumes?

backup/volutil seems to want to be root (I haven't managed to get it
to work, but I only tried for 5 minutes).  If true, the amandaish
solution is to have a run-codabackup program that is suid - see
libexec/runtar in amanda's $(prefix).

I don't see why they need to be root; perhaps they just need to be
able to get at the token files so they can authenticate to codasrv.

-- 
        Greg Troxel <gdt_at_ir.bbn.com>