# How do you add an EC2 instance created with ec2 module to ~/.ssh/known\_hosts

**URL:** <https://forum.ansible.com/t/how-do-you-add-an-ec2-instance-created-with-ec2-module-to-ssh-known-hosts/27181>\
**Category:** Ansible Project\
**Tags:** ubuntu\
**Created:** [April 3, 2018, 5:36pm UTC](https://forum.ansible.com/t/how-do-you-add-an-ec2-instance-created-with-ec2-module-to-ssh-known-hosts/27181 "2018-04-03T17:36:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Tim\_Stewart](https://avatars.discourse-cdn.com/v4/letter/t/13edae/32.png) [@Tim\_Stewart](https://forum.ansible.com/u/Tim_Stewart)\
**Post date:** [April 3, 2018, 5:36pm UTC](https://forum.ansible.com/t/how-do-you-add-an-ec2-instance-created-with-ec2-module-to-ssh-known-hosts/27181/1 "2018-04-03T17:36:46Z")

</div>

Let’s say I have this ec2 task (taken from the documentation) in a file named site.yml:

> `
> 
> # Basic provisioning example
> 
> - ec2:  
> key\_name: mykey  
> instance\_type: t2.micro  
> image: ami-123456  
> wait: yes  
> group: webserver  
> count: 3  
> vpc\_subnet\_id: subnet-29e63245  
> assign\_public\_ip: yes  
> `

Assuming I register the ec2 module result into a variable named ec2\_instances, what would I do to add that single ec2 instance to my ~/.ssh/known\_hosts file so that I can easily ssh into the new instance?

I’ve looked at the [known\_hosts](https://docs.ansible.com/ansible/2.5/modules/known_hosts_module.html) module and its example is:

> `
> 
> - name: tell the host about our servers it might want to ssh to  
> known\_hosts:  
> path: /etc/ssh/ssh\_known\_hosts  
> name: foo.com.invalid  
> key: “{{ lookup(‘file’, ‘pubkeys/foo.com.invalid’) }}”  
> `

Every property makes sense to me except for the key property. Regarding the lookup plugin, I don’t have any file containing public keys for my new instance (that I know of). What should I provide for the key property?

The documentation for the key property is:

> The SSH public host key, as a string (required if state=present, optional when state=absent, in which case all keys for the host are removed). The key must be in the right format for ssh (see sshd(8), section “SSH\_KNOWN\_HOSTS FILE FORMAT”)

I have looked into the sshd(8) [manual entry](http://manpages.ubuntu.com/manpages/bionic/man8/sshd.8.html) and here are the relevant paragraphs (emphasis mine):

> Each line in these files contains the following fields: markers (optional), hostnames, keytype, base64-encoded key, comment. The fields are separated by spaces.
> 
> The **keytype** and base64-encoded **key** are taken directly from the host key; they can be obtained, for example, from /etc/ssh/ssh\_host\_rsa\_key.pub. The optional comment field continues to the end of the line, and is not used.

How do I get the key I need to add to the file? This sounds like a common task so before I put forth potentially unnecessary effort to build my own solution, I thought I’d check to see if I was just missing something.

Thanks!