macOS mount to openBSD NFS shares

I have been using Vagrant & Virtualbox for a long time but recently I’ve run into something which I believe is a bug somewhere betweek macOS, nfsd, Virtualbox & openBSD.


The issue started after upgrading OSX to macOS Sierra, Virtualbox to 5.1.8 & Vagrant to 1.6.8. What were the issue and the facts?

  • I was creating shared folders through the Vagrantfile which exported them from macOS to openBSD
  • openBSD was mounting drives from shared directories in macOS
  • After accessing the openBSD “side” of shares, everything worked fine as usual.
  • But when I was trying to do something that made significant access to the share, macOS crashed and rebooted.
  • I must have worked on this for about ~20 hours
  • Macbook must have been restarted about ~40 times

Some of the things I’ve tried:

  • Used the default supported sharing system of virtualbox which is RSync for openBSD. This is one-way sync and very slow so not exactly what I wanted. We got also a strange merge in our git repository because it seemed that things were re-commited and I suspect RSync for this. Virtualbox does not support its 2-way sync in openBSD but even If it could, it’s very slow.
  • Used every setting I could and was supported in Vagrant/Virtualbox/nfsd related to the NFS shares, among them different NFS versions, TCP/UDP etc.
  • Tried to use samba as an alternative. I didn’t think to add the shares to the /etc/fstab file so I was unsuccessfully trying to make them work with sharing-light and usmb packages.
  • I tried almost every Virtualbox and Vagrant versions combination. What finally worked was downgrading to Vagrant 1.7.4 and Virtualbox 5.0.18. But not for quite long, because after 2 days, I tried to untar an 140MB tarball file and then the issue reappeared.
  • Installed the latest Virtualbox test build in case it has been solved. Failed.
  • Installed Virtualbox from the official downloaded packages. Uninstalled and install it again by homebrew. Failed.
  • I installed Vagrant & Virtualbox on my Kali Linux v2.0 laptop. A lot of identical issues on the debian/ubuntu bugtrackers. Finally after 1 hour I was able to make it work. Everything worked fine with all tools and NFS. Apparently this confirmed a compatibility issue of Virtualbox with macOS, running openBSD as a guest.
  • Changed network interfaces from the Virtualbox settings page. Checked virtualisation settings in BIOS.
  • Installed openBSD 5.9 & 6.0. No change.

There are a lot of bugs regarding compatibility of Vagrant and Virtualbox. Among them, Vagrant <1.8.6 seem to support Virtualbox 5.0.18 but it doesn’t. I was getting a message telling me that I need to install a Virtualbox version >4.x when I’ve already had installed 5.0.18.

Then I tried to upgrade Virtualbox to 5.0.20 and the problem came up again in its full extend. It seems that something has changed around 5.0.18–5.0.20 that broke the compatibility between Virtualbox, nfsd and macOS. There was no hope. Then a colleague suggested to try something like reversing the NFS shares. This is how I tried that:

  • I used sudo vifs in macOS to change the /etc/fstab file in order to add the mount to the NFS share: /Users/username/shared_dir nfs resvport
  • I added an export to the /etc/exports file in openBSD:
/home/vagrant/shared_dir/ -network=192.168.10 -mask= -alldirs -mapall=<your_username_here>
rcctl enable portmap mountd nfsd
rcctl set nfsd flags -tun 4
# after making changes to the export file
rcctl reload mountd
  • I mounted all the fstab included drives in macOS
mount -a

And finally I was able to share the directory I wanted from openBSD to macOS.

But I had a problem with permissions on macOS which was that I couldn’t read or write to the share. I created a user with the same username in openBSD and assigned him the same uid and gid with macOS. I don’t know If there are arguments to add uid/gid to a user in a simple command (e.g. adduser) but as far as this worked I’m fine:

# to get the id info of the user, do this both in openBSD and macOS.
# in my case they were uid=502, gid=20
id my_username
# create a user in openBSD with the same name as in macOS
useradd my_username
# assign uid and gid
usermod -u 502 my_username
usermod -g 20 my_username

and everything from this point worked perfectly!