How can I get the ssh host key for a new Azure Linux VM created using PowerShell?

Question

If I create an Azure Linux VM using PowerShell, how can I get its new ssh host key, so that I can install it in my local ssh/putty? Preferably the solution is also PowerShell code.

Answer 1

Old question, but for newcomers there is nowadays an alternative available by using run-command in Azure CLI. There is probably an equivalent for PowerShell too, but I have not investigated that.

az vm run-command invoke --name <your-vm-name> --command-id RunShellScript --scripts "cat /etc/ssh/ssh_host_ecdsa_key.pub"

will output a json document from which you can extract the public key. Beware though that this process is incredibly slow (~30 seconds per host), but you only need to run it once. See this gist for an example of how to update the known_hosts file with Ansible.

Answer 2

You can use a new "Run Command" feature of Azure Portal.

• In your Virtual Machine page, go to "Run command" in "Operations" section of VM menu.
• Select "RunShellScript" command.

• Paste the following command:

  for f in /etc/ssh/ssh_host_*_key; do ssh-keygen -l -f "$f"; done
  

• You will get an output like:

  Enable succeeded: 
  [stdout]
  256 SHA256:bKKCom8yh5gOuBNWaHHJ3rrnRXmCOAyPN/WximYEPAU /etc/ssh/ssh_host_ecdsa_key.pub (ECDSA)
  256 SHA256:IYeDl+gseYk46Acg4g2mcXGvCr7Z8FqOd+pCJz/KLHg /etc/ssh/ssh_host_ed25519_key.pub (ED25519)
  2048 SHA256:rA0lIXvHqFq7VHKQCqHwjsj28kw+tO0g/X4KnPpEjMk root@myazurevm (RSA)
  
  [stderr] 
  

  (the set of key types will vary with your VM image)

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The feature can also be used via Azure CLI, what is shown in the link above and also in the answer by @mwik.

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Check also my complete guide to Connecting securely to Microsoft Azure service with SFTP.