SSH - Not able to ssh from my laptop to raspberry after rebooting the pi

Question

Greetings to the community!

I am struggling establishing an ssh connection from laptop (Windows 10) to my pi connected to it through an Ethernet cable (raspberry pi 3 model B+).

The process I am following is the above one:

1) Flashing an image (more specifically, this one) to my SD card

2) Go to the /etc/network/interfaces file of the image and added the following lines of code

auto eth0
iface eth0 inet dhcp

so that my pi takes a dynamic ip from the dhcp.

3) Add the SD card in my pi, connect my pi through Ethernet cable into my laptop and boot (Network Sharing is enabled in Windows options)

4) Get the static IP(192.168.137.85) of my pi assigned to it and connect to it through SSH using Putty successfully

So far so good....

Unfortunately, if I reboot my pi (unplugged it or whatever - of course after I have previously ended the SSH connection) and I try again to establish an SSH connection with it, it fails.

The workaround currently is repeat the procedure above(flash again the image etc.), but this is not a real solution..

Any idea what could possibly be the reason for the failed ssh connection after the pi reboot? Thanks in advance

Answer 1

Anything that stops the connection process is a possible cause.

• No physical Ethernet connection (bad cable, lose connector, switch off, etc.)

• Not connecting to the actual IP of the Pi (static vs DHCP)

• Pi is using an IP address already in use by another system on the same LAN

• Pi is hung, crashed, or failed to boot

• Windows firewall blocking ping (ICMP), ssh protocols (Pi firewalls usually off)

Successful ping from Windows to Pi means the above issues are not the problem. Additional things:

• Pi sshd service is not enabled and running

• Userid used for ssh login non-existent or locked on the pi

Adding another user interface, monitor/keyboard/mouse or serial cable is the easiest (and typical) way to debug these issues.

Another approach is capture debugging information when on Pi boot.

1. Put the SD card into a Linux computer and mount the second partition (the Pi's ext4 root partition).
2. Add lines to script /etc/rc.local to capture debugging information to a text file /var/log/netdebug.
3. Unmount and remove the SD card.
4. Insert the SD in the Pi and power on.
5. After a reasonable period of time, connect to the Pi.
6. If you can't login, power off, remove the SD card.
7. Again mount the SD card in a Linux computer and look at the saved debug messages in netdebug.

This method is time-consuming, but doesn't require additional hardware (assuming a Linux system exists to write the SD card in the first place). Following are example dash script lines to add to /etc/rc.local.

# Capture networking information
echo "# date" >/var/log/netdebug
date >>/var/log/netdebug
# Show network interfaces, MAC, IP addresses, status.
echo "\n# ip addr show" >>/var/log/netdebug
ip addr show >>/var/log/netdebug
# Show running (listening) TCP network services.
echo "\n# netstat -lptn" >>/var/log/netdebug
netstat -lptn >>/var/log/netdebug
# Show status of sshd service.
echo "\n# systemctl status sshd.service" >>/var/log/netdebug
systemctl status sshd.service >>/var/log/netdebug
# Show that Ethernet is working.
# Replace 192.168.1.1 with known valid IP on Pi's LAN.
echo "\n# ping -c 3 192.168.1.1" >>/var/log/netdebug
ping -c 3 192.168.1.1 >>/var/log/netdebug
# Show that DNS can translate "google.com" to an IP addres
# and that the Internet is reachable.
echo "\n# ping -c 3 google.com" >>/var/log/netdebug
ping -c 3 google.com >>/var/log/netdebug

Answer 2

Very probably, the PI was allocated a different IP address upon reboot. Since you are using DHCP the address can change. Assuming the default name of your PI is raspberrypi and you have Mdns aka Zeroconf aka Bonjour running on your Windows machine, you may be able to use a local hostname instead of an IP address.

In case you have Itunes installed on your computer, I think it comes with Bonjour.

Try: ping raspberrypi.local.

Otherwise, if you turn on network discovery or use a port scanner, you should be able to locate the PI and determine its current IP address.

Answer 3

I had similar issues using an iPhone as the wifi broadcaster. Sometimes I could connect through ssh, sometimes I couldn't although I could still ping the device (raspberry pi zero w).

Turning ON "Maximize Compatibility" allowed me to ssh reliably from my laptop.