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124 lines
4.6 KiB
ReStructuredText
.. _connections:
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******************************
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Connection methods and details
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******************************
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This section shows you how to expand and refine the connection methods Ansible uses for your inventory.
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ControlPersist and paramiko
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---------------------------
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By default, Ansible uses native OpenSSH, because it supports ControlPersist (a performance feature), Kerberos, and options in ``~/.ssh/config`` such as Jump Host setup. If your control machine uses an older version of OpenSSH that does not support ControlPersist, Ansible will fallback to a Python implementation of OpenSSH called 'paramiko'.
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.. _connection_set_user:
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Setting a remote user
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---------------------
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By default, Ansible connects to all remote devices with the user name you are using on the control node. If that user name does not exist on a remote device, you can set a different user name for the connection. If you just need to do some tasks as a different user, look at :ref:`become`. You can set the connection user in a playbook:
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.. code-block:: yaml
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---
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- name: update webservers
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hosts: webservers
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remote_user: admin
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tasks:
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- name: thing to do first in this playbook
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. . .
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as a host variable in inventory:
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.. code-block:: text
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other1.example.com ansible_connection=ssh ansible_user=myuser
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other2.example.com ansible_connection=ssh ansible_user=myotheruser
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or as a group variable in inventory:
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.. code-block:: yaml
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cloud:
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hosts:
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cloud1: my_backup.cloud.com
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cloud2: my_backup2.cloud.com
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vars:
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ansible_user: admin
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.. seealso::
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:ref:`ssh_connection`
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Details on the ``remote_user`` keyword and ``ansible_user`` variable.
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:ref:`general_precedence_rules`
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Details on Ansible precedence rules.
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Setting up SSH keys
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-------------------
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By default, Ansible assumes you are using SSH keys to connect to remote machines. SSH keys are encouraged, but you can use password authentication if needed with the ``--ask-pass`` option. If you need to provide a password for :ref:`privilege escalation <become>` (sudo, pbrun, and so on), use ``--ask-become-pass``.
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.. include:: shared_snippets/SSH_password_prompt.txt
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To set up SSH agent to avoid retyping passwords, you can do:
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.. code-block:: bash
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$ ssh-agent bash
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$ ssh-add ~/.ssh/id_rsa
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Depending on your setup, you may wish to use Ansible's ``--private-key`` command line option to specify a pem file instead. You can also add the private key file:
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.. code-block:: bash
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$ ssh-agent bash
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$ ssh-add ~/.ssh/keypair.pem
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Another way to add private key files without using ssh-agent is using ``ansible_ssh_private_key_file`` in an inventory file as explained here: :ref:`intro_inventory`.
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Running against localhost
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-------------------------
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You can run commands against the control node by using "localhost" or "127.0.0.1" for the server name:
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.. code-block:: bash
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$ ansible localhost -m ping -e 'ansible_python_interpreter="/usr/bin/env python"'
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You can specify localhost explicitly by adding this to your inventory file:
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.. code-block:: bash
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localhost ansible_connection=local ansible_python_interpreter="/usr/bin/env python"
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.. _host_key_checking_on:
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Managing host key checking
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--------------------------
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Ansible enables host key checking by default. Checking host keys guards against server spoofing and man-in-the-middle attacks, but it does require some maintenance.
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If a host is reinstalled and has a different key in 'known_hosts', this will result in an error message until corrected. If a new host is not in 'known_hosts' your control node may prompt for confirmation of the key, which results in an interactive experience if using Ansible, from say, cron. You might not want this.
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If you understand the implications and wish to disable this behavior, you can do so by editing ``/etc/ansible/ansible.cfg`` or ``~/.ansible.cfg``:
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.. code-block:: text
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[defaults]
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host_key_checking = False
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Alternatively this can be set by the :envvar:`ANSIBLE_HOST_KEY_CHECKING` environment variable:
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.. code-block:: bash
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$ export ANSIBLE_HOST_KEY_CHECKING=False
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Also note that host key checking in paramiko mode is reasonably slow, therefore switching to 'ssh' is also recommended when using this feature.
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Other connection methods
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------------------------
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Ansible can use a variety of connection methods beyond SSH. You can select any connection plugin, including managing things locally and managing chroot, lxc, and jail containers.
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A mode called 'ansible-pull' can also invert the system and have systems 'phone home' via scheduled git checkouts to pull configuration directives from a central repository.
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