This. I cannot stress how important both of these factors are.

I still haven't found a solution other than (http://meocloud.pt, which was implemented by my former colleagues) that was within an order of magnitude as fast and/or as light in terms of CPU load, _and_ that supported Linux directly (let alone had halfway decent MacOS support).

Look into Syncthing. It's free and libre and works excellently as a replacement.

If you're up for a self-hosted option, Seafile is great. The server and the client are both pretty lightweight. You should create and store encrypted volumes yourself and not trust its encryption mechanism, but it handles delta sync very well, which means it's only sending the pieces that change (and e.g. a Veracrypt/Truecrypt volume doesn't change a lot when adding/removing data from a volume, so you won't sync a lot for example with OwnCloud, which also has the nasty habit of eating your files).

I've had significant issues attempting to run dropbox headless on the server for file syncing. We needed to include files from another group that was used to primarily working in Dropbox in a daily report build, and so our first go at it was to just run dropbox on that machine and pull the files directly from there. Long story short, the Dropbox client crashed periodically and would stop syncing due to issues with its local state.

After setting up monitoring around the client to keep it running we wound up switching to a different, more reliable solution.

Dropbox works ok on the server but I wouldn't rely on it as a step in any important workflows unless the client has improved significantly in the past year.

It's interesting to read this as I've had instances running on servers for years without having to be restarted. That's on Ubuntu. Maybe the binaries they distribute aren't adequately tested on other distros?

I didn't think Dropbox was meant for use on servers. I can see reasons why you would, but it seems like mapping a drive / mounting a share / etc would be better suited for accessing files on a server.

There's a version that can be run on a linux server without X installed. IIRC Dropbox provides it, but doesn't really support or make any promises wrt its reliability.

If all you need is folder/volume sharing between two machines, samba or nfs (or something similar) works great, but as I mentioned the reason for attempting to use dropbox in that fashion was to integrate with a workflow already being used by another team.

I'd rather pay for privacy and security with compute cycles. To whom else do you give your root password and hope that nothing bad happens?