Ubuntu/Debian and nfs mount issue solved

I spent a while trying to figure this one out: nfs client mounts were very slow on one of my servers. The dmesg output kept saying:

portmap: server localhost not responding, timed out
RPC: failed to contact portmap (errno -5).

Also, rpcinfo was not working for me:

~$ sudo rpcinfo -p 127.0.0.1
rpcinfo: can't contact portmapper: RPC: Remote system error - Connection refused
~$ sudo rpcinfo -p localhost
rpcinfo: can't contact portmapper: RPC: Remote system error - Connection refused

NFS mounts were working but were extremely slow:

~$ sudo mount hostname:/path

...

I was convinced that the problem lied with my hosts file, firewall, or hosts.allow or hosts.deny. It turns out that the problem was simply that a few packages had to be installed:

~$ sudo apt-get install nfs-common
...
Selecting previously deselected package libevent1.
Selecting previously deselected package libnfsidmap1.
Selecting previously deselected package nfs-common.