Raspberry pi always stops responding to SSH after some hours powered

Question

I've had this problem with all my raspberry pi's: they simply stop responding to SSH, VNC and other things, after some time. When this happens, I go to my router configuraton page and I can see the raspberry pi is connected. Then, when I restart the Pi, of course it works, but after some hours, I know the problem will happen again.

This always happens to me. I really wish my raspberry pi were 100% of the time connected and able to serve me things.

Answer 1

Stuff like this can be really tedious to peg down, since unless you have a keyboard and monitor you can plug in, there's no way, if ssh doesn't work, to check what's gone wrong on the live system.

Here's a simple starting point:

#!/bin/bash

# Set these to whatever you want.
router_ip=192.168.0.1
log_file=/tmp/mystery.log

# Make sure we can write to the log.
touch $log_file
if [ $? != 0 ]; then
    echo "Cannot use $log_file."
    exit 1
fi  

# Redirect output.
exec 1> /dev/null
exec 2>> $log_file

# A function for logging.
print2log () {
    echo $(date +"%D %R ")$@ >>$log_file
}

# Loop infinitely.
while [ 1 ]; do
    sleep 900 # 15 minutes
    # Ping router.
    ping -c 1 $router_ip & wait $!
    if [ $? != 0 ]; then
        print2log "Ping $router_ip failed."
    else print2log "Ping OK."
    fi
    # Check sshd.
    print2log "sshd PIDs: "$(ps -o pid= -C sshd)
done

Call this check.sh or whatever you want, chmod 755 check.sh to make it executable, and start it from within an ssh login:

setsid ./check.sh &

It does not have to be run sudo. You can now log out and that should stay going. Every 15 minutes it will print something like this to /tmp/mystery.log:

03/27/15 10:59 Ping OK.
03/27/15 10:59 sshd PIDs: 4261 14262

The first line indicates there is a working network connection and the second one indicates sshd is running. WRT those PIDs: there should be at least one, and while exactly what it is doesn't matter, it should be reasonably consistent (i.e., not change every 15 minutes).

If there are no PIDs at a certain point, you have at least confirmed that sshd has died for some reason.

grep sshd /var/log/syslog

Should help you find the reason.

Answer 2

I once had the same problem: no connection over WiFi anymore. In my case, the WiFi dongle was sent to sleep after a certain time of inactivity and couldn't be woke up remotely (obviously). As solution I had to deactivate the powermanagement for the WiFi dongle.

EDIT:

I was using an Edimax WiFi dongle on Arch Linux, and to disable power management, I needed to add the following line to /etc/modules

options 8192cu rtw_power_mgnt=0

Answer 3

I usually have this problem on remote hosts but look at client avile interval and client avile max count: http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man5/sshd_config.5?query=sshd%5fconfig&sec=5