My PC, my ‘headless’ Raspberry Pi (user me), and my brother’s PC (user him) are all on my Zerotier network. After using ssh to get a command line interface to the Pi, I run…
rsync -avP --append-verify “[source file on Pi]” him@192.168.nnn.nnn:[destination folder on his PC]
…after which I press Ctrl/Z followed by bg and then disown to detach from the file copying process, then I can exit from the Pi and turn my computer off. The Pi can just chug away copying the specified file - potentially for many hours.
If anything goes wrong, when I reboot the Pi I just repeat that rsync command, and the file transfer continues from where it left off.
BUT when I use ssh to try and connect to him (either directly from my PC, or indirectly through the Pi, after opening another ssh interface), ssh hangs without getting as far as prompting for a password.
After rebooting the Pi, I can successfully ssh to him (from Pi or PC) if I do this before re-starting the rsync command, but it won’t work if the rsync job is already running (regardless of whether I detach using Ctrl/Z - bg - disown, or just leave that Pi command window open on my PC).
Why does running rsync (on my Pi, copying a file to his PC) prevent me from establishing an ssh connection to his PC? Is there anything I can do to get round this?