how to define ssh private key for servers fetched by dynamic inventory in files

Question

I met one configuration problem when coding ansible playbook for ssh private key file.

As we know, we can define combination with host server, ip & related ssh private key in ansible hosts file for static inventory servers.

But i have no idea how to define that with dynamic inventory servers.

Ex:

---
- hosts: tag_Name_server1
  gather_facts: no
  roles:
    - role1

- hosts: tag_Name_server2
  gather_facts: no
  roles:
    - roles2

Below command is used to call that playbook:

ansible-playbook test.yml -i ec2.py --private-key ~/.ssh/SSHKEY.pem

My question is:

How can i define ~/.ssh/SSHKEY.pem in ansible files rather then in command line
I guess there might be one parameter in playbook like "gather_facts" to define which private key should be used for above hosts, but there looks like no such parameter?
If there is no way to define private key in files, what should be defined in command line if different key file will be used for different dynamic fetched servers for one playbook?

Thank you for your comments

User · Answer

You can simply define the key to use directly when running the command:

ansible-playbook \
        \ # Super verbose output incl. SSH-Details:
    -vvvv \
        \ # The Server to target: (Keep the trailing comma!)
    -i "000.000.0.000," \
        \ # Define the key to use:
    --private-key=~/.ssh/id_rsa_ansible \
        \ # The `env` var is needed if `python` is not available:
    -e 'ansible_python_interpreter=/usr/bin/python3' \ # Needed if `python` is not available
        \ # Dry–Run:
    --check \
    deploy.yml

Copy/ Paste:

ansible-playbook -vvvv --private-key=/Users/you/.ssh/your_key deploy.yml

User · Answer

TL DR  Specify key file in group variable file  since  tag Name server1  is a group     Note  I m assuming you re using the EC2 external inventory script  If you re using some other dynamic inventory approach  you might need to tweak this solution   This is an issue I ve been struggling with  on and off  for months  and I ve finally found a solution  thanks to Brian Coca s suggestion here  The trick is to use Ansible s group variable mechanisms to automatically pass along the correct SSH key file for the machine you re working with   The EC2 inventory script automatically sets up various groups that you can use to refer to hosts  You re using this in your playbook  in the first play  you re telling Ansible to apply  role1  to the entire  tag Name server1  group  We want to direct Ansible to use a specific SSH key for any host in the  tag Name server1  group  which is where group variable files come in   Assuming that your playbook is located in the  my-playbooks  directory  create files for each group under the  group vars  directory   my-playbooks  -- test yml  -- group vars       -- tag Name server1 yml       -- tag Name server2 yml   Now  any time you refer to these groups in a playbook  Ansible will check the appropriate files  and load any variables you ve defined there   Within each group var file  we can specify the key file to use for connecting to hosts in the group     tag Name server1 yml   --------------------      Variables for EC2 instances named  server1  --- ansible ssh private key file   path to ssh key server1 pem   Now  when you run your playbook  it should automatically pick up the right keys     Using environment vars for portability  I often run playbooks on many different servers  local  remote build server  etc    so I like to parameterize things  Rather than using a fixed path  I have an environment variable called SSH KEYDIR that points to the directory where the SSH keys are stored   In this case  my group vars files look like this  instead     tag Name server1 yml   --------------------      Variables for EC2 instances named  server1  --- ansible ssh private key file      lookup  env   SSH KEYDIR      server1 pem      Further Improvements  There s probably a bunch of neat ways this could be improved  For one thing  you still need to manually specify which key to use for each group  Since the EC2 inventory script includes details about the keypair used for each server  there s probably a way to get the key name directly from the script itself  In that case  you could supply the directory the keys are located in  as above   and have it choose the correct keys based on the inventory data

User · Answer

I had a similar issue and solved it with a patch to ec2.py and adding some configuration parameters to ec2.ini. The patch takes the value of ec2_key_name, prefixes it with the ssh_key_path, and adds the ssh_key_suffix to the end, and writes out ansible_ssh_private_key_file as this value.

The following variables have to be added to ec2.ini in a new 'ssh' section (this is optional if the defaults match your environment):

[ssh]
# Set the path and suffix for the ssh keys
ssh_key_path = ~/.ssh
ssh_key_suffix = .pem

Here is the patch for ec2.py:

204a205,206
>     'ssh_key_path': '~/.ssh',
>     'ssh_key_suffix': '.pem',
422a425,428
>         # SSH key setup
>         self.ssh_key_path = os.path.expanduser(config.get('ssh', 'ssh_key_path'))
>         self.ssh_key_suffix = config.get('ssh', 'ssh_key_suffix')
> 
1490a1497
>         instance_vars["ansible_ssh_private_key_file"] = os.path.join(self.ssh_key_path, instance_vars["ec2_key_name"] + self.ssh_key_suffix)

User · Answer

I m using the following configuration    site yml  - name  Example play   hosts  all   remote user  ansible   become  yes   become method  sudo   vars      ansible ssh private key file    home ansible  ssh id rsa

User · Answer

The best solution I could find for this problem is to specify private key file in ansible.cfg (I usually keep it in the same folder as a playbook):

[defaults]
inventory=ec2.py
vault_password_file = ~/.vault_pass.txt
host_key_checking = False
private_key_file = /Users/eric/.ssh/secret_key_rsa

Though, it still sets private key globally for all hosts in playbook.

Note: You have to specify full path to the key file - ~user/.ssh/some_key_rsa silently ignored.

[ansible] how to define ssh private key for servers fetched by dynamic inventory in files

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