mjhjmtu

Setup: remote server running Debian 9 (no GUI).

Normally, I run transmission-cli without any issues. I want to have transmission-cli save to a remote location. The remote location has plenty of available disk space (I just double-checked with df -h).

This is what I do:

[···]$ sshfs my.remote.server.com:/dir/on/remote/server /home/cal-linux/remote -oallow_other
[···]$ chmod 777 /home/cal-linux/remote

Then, I run transmission-cli as follows:

[···]$ transmission-cli -ep -w /home/cal-linux/remote <magnet-link>

It won't work. This is the output (edited to remove timestamps and IDs and replace the torrent name):

[2018-12-15 ··· ] Transmission 2.92 (14714) started
[2018-12-15 ··· ] RPC Server: Adding address to whitelist: 127.0.0.1
[2018-12-15 ··· ] DHT: Generating new id
[2018-12-15 ··· ] Saved "/home/cal-linux/.config/transmission/torrents/the-torrent.xxxx.torrent"
[2018-12-15 ··· ] Port Forwarding (NAT-PMP): initnatpmp succeeded (0)
[2018-12-15 ··· ] Port Forwarding (NAT-PMP): sendpublicaddressrequest succeeded (2)
Progress: 0.0%, dl from 0 of 0 peers (0 kB/s), ul to 0 (0 kB/s) [None] [2018-12-15 ··· ] Port Forwarding: State changed from "Not forwarded" to "Starting"
Progress: 0.0%, dl from 15 of 15 peers (0 kB/s), ul to 0 (0 kB/s) [N[2018-12-15 ··· ] the-torrent: Starting IPv4 DHT announce (poor, 15 nodes)
[2018-12-15 ··· ] Saved "/home/cal-linux/.config/transmission/torrents/the-torrent.xxxx.torrent"
[2018-12-15 ··· ] the-torrent: Pausing
[2018-12-15 ··· ] Saved "/home/cal-linux/.config/transmission/settings.json"
Progress: 0.0%, dl from 22 of 22 peers (0 kB/s), ul to 0 (0 kB/s) [None] 
[2018-12-15 ··· ] Saved "/home/cal-linux/.config/transmission/resume/the-torrent.resume"
[2018-12-15 ··· ] the-torrent: Magnet Verify
[2018-12-15 ··· ] the-torrent: Queued for verification
[2018-12-15 ··· ] DHT: Not saving nodes, DHT not ready
[2018-12-15 ··· ] Port Forwarding: Stopped
[2018-12-15 ··· ] the-torrent: Removing torrent
[2018-12-15 ··· ] the-torrent: Pausing

I was originally getting the errors:

UDP: Failed to set receive buffer: requested 4194304, got 425984
UDP: Please add the line "net.core.rmem_max = 4194304" to /etc/sysctl.conf

and similar for wmem_max, but I added the suggested lines to /etc/sysctl.conf and rebooted. Now I don't get those errors, but it still won't work (the above output is after making the changes to sysctl.conf).

Any suggestions?

It seems that both your transmission and sshfs work well. As is said in your question, you are downloading (or seeding) with a magnet link. This requires DHT to download the torrent from peers. If there is no client let you download the torrent file they have, you will never get the torrent file and start the real download.