I have a QNAP TS-251 NAS with a pair of 4 GB drives set up as RAID 1, running as a server, mainly for backups. It has the default operating system, QTS 4.2.0 (2016/01/19), which I think is current. It's a customized flavor of Linux with a GUI interface that I run from my Windows desktop. It has IP number 169.254.100.101 on its Ethernet #1 port and 169.254.100.102 on its Ethernet #2 port.
As a client, I have an old Dell (Core 2 Duo T8100) laptop running Ubuntu 14.04 LTS. It's connected to the QNAP's #2 Ethernet port, and its IP number is 169.254.100.99.
Note: From here I'll include background details that can probably be skipped (but answer "Why would you do this?" questions I anticipate) in [brackets].
There's also a Windows desktop connected to the QNAP's #1 Ethernet port, which is involved with this only to run the QNAP's GUI. I can also use PuTTY from it to the QNAP if I need a command line
[The QNAP comes with several default shared folders: Download, Multimedia, Public, Recordings, Web, homes.]
I created a shared folder named CrashPlan on the QNAP server, and a mount point on the Ubuntu client named /mnt/QNAP-CrashPlan. I installed NFS client packages on the client with
sudo apt-get install portmap nfs-client [and installed autofs with
sudo apt-get install autofs in an unsuccessful attempt to diagnose problems].
Following advice in this question, I gave NFS access rights, host/IP/network 169.254.*, permission read/write, and squash option NO_ROOT_SQUASH. The anonymous boxes remained grayed out.
So, in the moment of truth, from the client, I tried
sudo mount 169.254.100.102:/CrashPlan /mnt/QNAP-CrashPlan and
sudo mount -t nfs 169.254.100.102:/CrashPlan /mnt/QNAP-CrashPlan, and got
mount.nfs: Connection timed out in both cases.
In an attempt to diagnose the problem, I tried
showmount -e 169.254.100.102, but it replied
clnt_create: RPC: Port mapper failure - Unable to receive: errno 111 (Connection refused).
I've searched a lot and tried a lot, but I haven't found any further paths to diagnose the problem. Any ideas?
I will edit in more details as needed. Also, this might deserve a "qnap" tag, but I don't have create tag permission.
[XY problem details: The reason I named the shared folder that I created CrashPlan is that I tried to run the QNAP as a CrashPlan server. I wasn't able to get that to work except by mounting the CrashPlan folder as a Windows drive, using
net use to mount it, and running a separate user-mode client instance of CrashPlan on Windows, because Windows doesn't allow services access to
net use drives. Running the CrashPlan server on my old Ubuntu laptop with the QNAP mounted through NFS was described as a configuration that avoided that issue.]