While mounting our NFS at /home/ is convenient for users to share their data between machines relatively transparently, there are some issues that crop up from time to time. I want to document a list of these issues and mitigations that I’ve come up with, so I’ll put that here.

  • opam can’t enable switches: It seems that opam is not designed to run on an NFS, or maybe more precisely, our NFS has too high latency for opam to work well. As such, putting your OPAMROOT on a different filesystem (namely /scratch) is recommended. This can be done by adding the following line to your .bashrc, .zshrc, etc: 
    export OPAMROOT=/scratch/$USER/.opam

    Alternatively, you can check out something like nfsopam.sh.

  • ghc via ghcup: ghcup is the recommended tool to manage ghc versions. Upon install, it reads the environment variable GHCUP_INSTALL_BASE_PREFIX, which allows you to select an alternative base installation location, probably a good idea, because Haskell compilation is already slow enough. Notably, this needs to be set when running ghcup commands as well as during install, so it is best to put this in your .bashrc/.zshrc/etc: 
    export GHCUP_INSTALL_BASE_PREFIX=/scratch/$USER