I am running a CoreOS EC2 instance. I run a process on this instance that listens on local port 950. Usually, everything works fine, but after a recent reboot of the CoreOS server the process could not listen on port 950 because it was already taken by another process.
This other process appears to be an NFSv4 client that is used to mount an AWS EFS volume. Here is what netstat tells me:
Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 10.30.102.250:950 10.30.102.170:2049 ESTABLISHED
Here is the relevant part of
fs-faa33256.efs.us-west-2.amazonaws.com:/ /efs nfs4 rw,relatime,vers=4.1,\ rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,\ clientaddr=10.30.102.250,local_lock=none,addr=10.30.102.170 0 0
A couple of questions: 1. Why is the NFS client on the CoreOS server using a low-numbered port to communicate with the remote NFSv4 server? 2. Can I tell the NFS client to avoid using port 950 (or use only non-privileged ports)?