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TL;DR: Can't SSH to my EC2 instance after upgrading Ubuntu.

I set up a EC2 instance with Bitnami Wordpress AMI. The image has Ubuntu 16.04 and I want Ubuntu 18.04 so I connected to the instance via SSH using PuTTY with

ubuntu@ec2-{ip}.compute-1.amazonaws.com

and once inside I did

sudo do-release-upgrade

During upgrade I was prompted to choose between updating or preserving ssh_config. I chose to preserve it because I wanted to use the SSH key I had set for the instance.

I was prompted to reboot the instance which I did. After reboot the server works (I can connect to it from my browser) but I can't connect via SSH. PuTTY error message is

Network error: Connection refused.

I did notice the ip changed after reboot and I did use the new ip when trying to connect.

Additionally: I don't know how to check the contents of ssh_config or if the SSH service is running without connecting via SSH.

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2
  • Try to obtain the console log. Check if the machine has booted. Can you access any service? Is it answering to ping?
    – Mircea Vutcovici
    Dec 25, 2019 at 7:27
  • @MirceaVutcovici The site is up so it has booted. From AWS console I can get system log. I notice it tries to start SSH multiple times but fails. Here is a relevant snippet pastebin.com/GSSEuVTi
    – Markus Uusitalo
    Dec 25, 2019 at 11:18

1 Answer 1

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You need to stop the VM and attach its disk to another new temporary VM. Then check the logs (journalctl -b --file=/path/to//var/log/journal/....). Fix the syntax error in /path/to/etc/ssh/sshd_config. Verify the sshd config with sshd -T -f /path/to/etc/ssh/sshd_config. Detach the disk, then try to boot again the machine.

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3
  • It seems an ubuntu instance will not persist the journal file. SSH is configured to log to AUTH, so /var/log/auth.log
    – Andy
    Dec 20, 2020 at 16:51
  • You can create /var/log/journal directory to make it persistent.
    – Mircea Vutcovici
    Dec 20, 2020 at 17:51
  • True, but we're talking about an investigation after the fact, so that doesn't help.
    – Andy
    Dec 20, 2020 at 17:53

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