Raspberry Pi 4 does not respond ssh

Question

My setup is a RaspberryPi4 with SSD (Kingston 120GB) as boot drive. It has also a regular HDD connected to it. Both hard drives are connected to a USB dock via 3.0 USB. The dock has also a power supply so no energy problems should arise. Connected via ethernet to router. SSH enabled. I have setup an apache server with Nextcloud (which it hasn't been started to be used because of the problems stated below) and also is setup as a client for a Wireguard VPN.

The problem is that when I turn on the RPi4 I can ssh to it without any issues, but if I leave it powered ON overnight, the next day I try to connect to it, the ssh console (or whatever I try to use) just freezes or behaves abnormally.

One day I could log in but I could not run any "complicated" commands (just cd and ls were working) and trying to run commands like sudo nano just left my ssh window frozen, no output. And today for example it just does not connect. I can ping the RPi4, but ssh refuses to let me in. It just freezes after inputting the password, no output from the RPi4.

I don't know what might be happening, this is the first time something like this happens to me, but I think it could be related to the USB dock with the hard drives in it? How can I know what is happening?

Answer 1

There are many possibilities, from a heavy load that is running to a faulty SD card.

First thing is to examine the logs. Does the syslog give any hints? Errors/warnings? If so: this is probably the first thing you need to correct.

Next would be the filesystems. Any at 100%? What about swap?

Can you run a vmstat 10 > /tmp/vmstat until it crashes? that would give some information about whether the system is extremely loaded. If the vmstat shows extreme load, you might try

#!/bin/bash

while : ; do
    top -bn1 >>/tmp/top
    sleep 10
done

(or put the output on some external drive if your sdcard is relatively full). That will give you an idea of the process that causes the load.

Answer 2

It could be that there is a heavy memory workload, so there is a lot of swapping. I had similiar issues when I executed too many programs at once.

Try disabling swapfile, then the heavy memory application should be killed more likely and ssh should be still available.

Try this day via sudo swapoff -a This disables swap until the next reboot.