Your Linux server’s network is maxed out, and you have no idea what’s eating it, so here’s how to find the exact program behind it in under 2 minutes using nethogs, iftop, ss, and the /proc filesystem.
This happens pretty often. The server starts feeling slow, uploads get stuck at 100 percent, or you notice your cloud bill creeping up without any clear reason.
You check top or htop, but everything looks fine because those tools only show CPU and memory, not network usage. So you know something is eating bandwidth, but you cannot actually see what it is.
Linux already has a few simple tools that can help with this. Once you get used to them, you can quickly spot the process behind the traffic instead of just guessing and restarting services randomly.