OSX NFS server, Linux client can't read mount

NFS server running on a Mac Powerbook, Linux client box on the LAN. I
can mount the share. fstab has
192.168.1.102:/Volumes/Alien /mnt/alien nfs
user,exec,rw,hard,intr 0 0

cat /proc/mounts
192.168.1.102:/Volumes/Alien /mnt/alien nfs
rw,nosuid,nodev,v3,rsize=16384,wsize=16384,hard,in tr,udp,lock,
addr=192.168.1.102 0 0

However, when I try to access /mnt/alien, I get

ls: reading directory /mnt/alien: Input/output error

I don't know if the problem's on the Linux side or the OSX, which I
don't know from shinola. Any advice as to why the mount can't be
accessed greatly appreciated. Thanks.

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