Ttgjyuk

How do I add an SSH key to a cloud instance?

I tried adding keys manually, but just couldn't connect.
Here's what I tried:

thufir@mordor:~$ 
thufir@mordor:~$ gcloud compute config-ssh
WARNING: The private SSH key file for Google Compute Engine does not exist.
WARNING: You do not have an SSH key for Google Compute Engine.
WARNING: [/usr/bin/ssh-keygen] will be executed to generate a key.
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/thufir/.ssh/google_compute_engine.
Your public key has been saved in /home/thufir/.ssh/google_compute_engine.pub.
The key fingerprint is:
SHA256:ioreurewiopruweoiprwe thufir@mordor
The key's randomart image is:
+---[RSA 2048]----+
.......
| |
| |
+----[SHA256]-----+

Updated [https://www.googleapis.com/compute/v1/projects/<project>].
You should now be able to use ssh/scp with your instances.
For example, try running:

 $ ssh <instance>.<location>.<project>

thufir@mordor:~$ 
thufir@mordor:~$ ssh <instance>.<location>.<project>
The authenticity of host 'compute.<####> (<ip address>)' can't be established.
ECDSA key fingerprint is SHA256:<fingerprint?>.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'compute.<####>' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-31-generic x86_64)

 * Documentation: https://help.ubuntu.com
 * Management: https://landscape.canonical.com
 * Support: https://ubuntu.com/advantage

 Get cloud support with Ubuntu Advantage Cloud Guest:
 http://www.ubuntu.com/business/services/cloud

0 packages can be updated.
0 updates are security updates.



The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

$ 
$ 
$ whoami
thufir
$ pwd
/home/thufir
$ exit
Connection to <ip address> closed.
thufir@mordor:~$ 

Probably a too late answer, but here it is

ssh-keygen -t rsa -f ~/.ssh/google_compute_engine -C <service-account>

Then

gcloud compute ssh <service-account> --command="bash xxxxxx"

You don't need to add it in user folder manually. Google Cloud will add it automatically every time you try to log in to your VM.
To permanently add SSH Key in a VM instance you can add your public key in metadata in the menu. Step wise step process is explained here.