I'm using Root.io's Trellis workflow.

I've encountered an error wherein I couldn't establish a connection via ansible-playbook.

  1. When I run ansible-playbook server.yml -e env=staging it throws me an error that the ssh connection cannot be established so I checked my users.yml file and saw a problem under the keys section:

    - name: "{{ admin_user }}"
        - sudo
        - "{{ lookup('file', '~/.ssh/id_rsa.pub') }}"
        - https://github.com/dummyuser.keys

    I realised I have an existing id_rsa.pub key but I didn't have it authorized on my server, I was using https://github.com/dummyuser.keys instead. So I removed that line

    - "{{ lookup('file', '~/.ssh/id_rsa.pub') }}"

    However the problem still persists. The response was:

    fatal: []: UNREACHABLE! => {
        "changed": false, 
        "msg": "Failed to connect to the host via ssh.", 
        "unreachable": true

    Also why does the config point to the public key when we need the private key to login via ssh. I usually do

    ssh -i ~/.ssh/private_key [email protected]

    whenever I login to the server via ssh.

  2. I So I used another approach. specified the key on the cli this time

    ansible-playbook server.yml -e env=staging -vvvv --key-file=~/.ssh/dummy_rsa

    and the result was I was able to establish a connection:


    But there was another error: it says a password is required here's the full message:

    fatal: []: FAILED! => {
        "changed": false, 
        "failed": true, 
        "invocation": {"module_name": "setup"}, 
        "module_stderr": "OpenSSH_6.9p1, LibreSSL 2.1.8\r\ndebug1: Reading configuration data /etc/ssh/ssh_config\r\ndebug1: /etc/ssh/ssh_config line 21: Applying options for *\r\ndebug1: auto-mux: Trying existing master\r\ndebug2: fd 3 setting O_NONBLOCK\r\ndebug2: mux_client_hello_exchange: master version 4\r\ndebug3: mux_client_forwards: request forwardings: 0 local, 0 remote\r\ndebug3: mux_client_request_session: entering\r\ndebug3: mux_client_request_alive: entering\r\ndebug3: mux_client_request_alive: done pid = 85702\r\ndebug3: mux_client_request_session: session request sent\r\ndebug1: mux_client_request_session: master session id: 2\r\ndebug3: mux_client_read_packet: read header failed: Broken pipe\r\ndebug2: Received exit status from master 1\r\nShared connection to closed.\r\n", 
        "module_stdout": "sudo: a password is required\r\n", 
        "msg": "MODULE FAILURE", 
        "parsed": false

    I'm not sure why it is asking for a password I've already set it in my group_vars/staging/vault.yml here's the content of that:

    vault_mysql_root_password: stagingpw
      dummy_admin: $6$rounds=656000$8DWzDN3KQkM9SjlF$DhxLkYaayplFmtj9q.EqzMDWmvlLNKsLU0GPL9E0P2EvkFQBsbjcMCXgWkug4a5E66PfwL4eZQXzMLkhXcPBk0
  3. So I finally got logged in using the command below:

    ansible-playbook server.yml -e env=staging -vvvv --key-file=~/.ssh/dummy_rsa --ask-become-pass

    after asking me for a password it works and provisions my server without problem.

Can anyone give light to this? Am I missing something? Let me know if you need more details.

2 Answers 2


I've also posted this question on discourse and @fullyint has answered it in detail. So I'm just posting a link for the answer and some excerpt

Helping Ansible and ssh to find the necessary private key

This means that you are manually specifying the private key with each ssh command, and yes, the corollary of manually specifying the private key with every ansible-playbook command is to add the --private-key= or key-file= option. However, you could save yourself some hassle by enabling ssh and ansible-playbook commands to automatically find and use your desired private key file. One approach would be to add an entry to your ssh config file, specifying the IdentityFile to be used with Host I'd recommend the alternative of loading the ~/.ssh/dummy_rsa into your ssh-agent, which can handle keys for you, trying multiple private keys when attempting a connection.
Make sure your ssh-agent is running: ssh-agent bash Add your key: ssh-add ~/.ssh/dummy_rsa If you're on mac, add the key to your Keychain: ssh-add -K ~/.ssh/dummy_rsa Now you should be able to run ssh commands without the -i option, and ansible-playbook commands without the --key-file= option because your ssh-agent will inform those commands of the various available private keys to try in making the ssh connections.

Reasons for the error "sudo: a password is required"

Of the tasks Trellis runs via the server.yml playbook, some require sudo. This is a non-issue when the playbook connects as root, but sometimes the playbook doesn't connect as root. If this initial connection attempt as root fails, it will fall back to connecting as the admin_user. This user must specify its sudo password via the option --ask-become-pass, as you discovered.
Maybe you already know why your connection as root failed, but here are some possibilities:
Maybe your remote is on AWS, where root is disabled by default, and your admin_user: ubuntu.
Maybe you've already successfully run server.yml with sshd_permit_root_login: false in group_vars/all/security.yml, so root is no longer allowed to log in via ssh (good security). Maybe the private key you are trying to use is not loaded on the remote in the root user's authorized_keys


You probably have not added your public key to the authorized_keys file inside the machine. You might also want to add your private key to your local SSH agent.

  1. Put your public key inside the server. Example for a key that is already on the server:

    # Add key directly on the box:
    echo "$(cat your_public_key)" >> ~/.ssh/authorized_keys
    # Add key from local to remote:
    ssh user@server "echo \"$(cat your_public_key)\" >> ~/.ssh/authorized_keys"
  2. You need to add the private key to your agent

    # Start agent
    eval "$(ssh-agent -s)"
    # Add private key
    ssh-add ~/.ssh/your_private_key
  • I know #1 and have already done it which is why I was able to connect by specifying my private key. Where should I do #2? On the server or on my local machine?
    – JohnnyQ
    Apr 21, 2016 at 22:45
  • Ah got it. I am in OSX so I used ssh-add -K ~/.ssh/dummy_rsa. What is the significance of adding the private key to the agent anyway?
    – JohnnyQ
    Apr 21, 2016 at 23:01
  • 1
    No need to type the password… the agent handles the negotiations with your SSH server on the other end. No man in the middle attacks anymore.
    – kaiser
    Apr 22, 2016 at 0:43
  • That is true. I also realised that it gives you the convenience to do ssh without having to specify your private key because you can do it this way ssh -i ~/.ssh/your_private_key [email protected]
    – JohnnyQ
    Apr 22, 2016 at 2:25
  • @JohnnyQ Normally you have a public/private key pair per server (and then for every service, bot, …). Therefore using the agent makes a ton of sense. You can add multiple keys and he will try them all on every SSH server he tries to connect to, negotiating access with a matching key.
    – kaiser
    Apr 22, 2016 at 11:58

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