Simon Peyton Jones
| Hmm. Here's a shot in the dark: is home home directory mounted via NFS by | any chance?
Direct hit! (for the shot in the dark). Yes it's NFS mounted I think. So what?
Well, as others have pointed out NFS and locking tends to be a bit of a can of worms. Some broken systems don't even run the locking daemon by default; even when configured properly locking can still be problematic, especially under contention (although I doubt this is the case in your situation). It's been quite a while since I have configured NFS, but IIRC one thing to verify is that there is at least one lockd process and one portmapper process running. I doubt this is problematic under Ubuntu in 2017, but it's worth checking. It might also be a good idea to grab an strace log of ghc-pkg to see what precisely is going on. Perhaps also check the system log. Regardless, we should try getting to the bottom of this; ghc-pkg failing is quite bad, even if the system's locking configuration happens to be broken. Cheers, - Ben