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302 lines
11 KiB
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Introduction To Ad-Hoc Commands
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===============================
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.. highlight:: bash
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The following examples show how to use `/usr/bin/ansible` for running
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ad hoc tasks.
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What's an ad-hoc command?
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An ad-hoc command is something that you might type in to do something really
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quick, but don't want to save for later.
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This is a good place to start to understand the basics of what ansible can do
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prior to learning the playbooks language -- ad-hoc commands can also be used
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to do quick things that you might not neccessarily want to write a full playbook
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for.
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Generally speaking, the true power of Ansible lies in playbooks.
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Why would you use ad-hoc tasks versus playbooks?
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For instance, if you wanted to power off all of your lab for Christmas vacation,
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you could execute a quick one-liner in Ansible without writing a playbook.
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For configuration management and deployments, though, you'll want to pick up on
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using '/usr/bin/ansible-playbook' -- the concepts you will learn here will
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port over directly to the playbook language.
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(See :doc:`playbooks` for more information about those)
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If you haven't read :doc:`intro_inventory` already, please look that over a bit first
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and then we'll get going.
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.. contents::
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:depth: 2
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.. _parallelism_and_shell_commands:
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Parallelism and Shell Commands
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``````````````````````````````
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Arbitrary example.
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Let's use ansible's command line tool to reboot all web servers in Atlanta, 10 at a time. First, let's
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set up SSH-agent so it can remember our credentials::
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$ ssh-agent bash
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$ ssh-add ~/.ssh/id_rsa
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If you don't want to use ssh-agent and want to instead SSH with a
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password instead of keys, you can with ``--ask-pass`` (``-k``), but
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it's much better to just use ssh-agent.
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Now to run the command on all servers in a group, in this case,
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*atlanta*, in 10 parallel forks::
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$ ansible atlanta -a "/sbin/reboot" -f 10
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/usr/bin/ansible will default to running from your user account. If you do not like this
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behavior, pass in "-u username". If you want to run commands as a different user, it looks like this::
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$ ansible atlanta -a "/usr/bin/foo" -u username
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Often you'll not want to just do things from your user account. If you want to run commands through sudo::
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$ ansible atlanta -a "/usr/bin/foo" -u username --sudo [--ask-sudo-pass]
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Use ``--ask-sudo-pass`` (``-K``) if you are not using passwordless
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sudo. This will interactively prompt you for the password to use.
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Use of passwordless sudo makes things easier to automate, but it's not
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required.
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It is also possible to sudo to a user other than root using
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``--sudo-user`` (``-U``)::
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$ ansible atlanta -a "/usr/bin/foo" -u username -U otheruser [--ask-sudo-pass]
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Ok, so those are basics. If you didn't read about patterns and groups yet, go back and read :doc:`intro_patterns`.
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The ``-f 10`` in the above specifies the usage of 10 simultaneous
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processes to use. You can also set this in :doc:`intro_configuration` to avoid setting it again. The default is actually 5, which
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is really small and conservative. You are probably going to want to talk to a lot more simultaneous hosts so feel free
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to crank this up. If you have more hosts than the value set for the fork count, Ansible will talk to them, but it will
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take a little longer. Feel free to push this value as high as your system can handle it!
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You can also select what ansible "module" you want to urn. Normally commands also take a ``-m`` for module name, but
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the default module name is 'command', so we didn't need to
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specify that all of the time. We'll use ``-m`` in later examples to
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run some other :doc:`modules`.
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.. note::
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The :ref:`command` module does not
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support shell variables and things like piping. If we want to execute a module using a
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shell, use the 'shell' module instead. Read more about the differences on the :doc:`modules`
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page.
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Using the :ref:`shell` module looks like this::
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$ ansible raleigh -m shell -a 'echo $TERM'
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When running any command with the ansible *ad hoc* CLI (as opposed to
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:doc:`playbooks`), pay particular attention to shell quoting rules, so
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the local shell doesn't eat a variable before it gets passed to Ansible.
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For example, using double vs single quotes in the above example would
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evaluate the variable on the box you were on.
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So far we've been demoing simple command execution, but most Ansible modules usually do not work like
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simple scripts. They make the remote system look like you state, and run the commands necessary to
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get it there. This is commonly referred to as 'idempotence', and is a core design goal of ansible.
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However, we also recognize that running arbitrary commands is equally important, so Ansible easily supports both.
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.. _file_transfer:
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File Transfer
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`````````````
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Here's another use case for the `/usr/bin/ansible` command line. Ansible can SCP lots of files to multiple machines in parallel.
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To transfer a file directly to many different servers::
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$ ansible atlanta -m copy -a "src=/etc/hosts dest=/tmp/hosts"
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If you use playbooks, you can also take advantage of the ``template`` module,
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which takes this another step further. (See module and playbook documentation).
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The ``file`` module allows changing ownership and permissions on files. These
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same options can be passed directly to the ``copy`` module as well::
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$ ansible webservers -m file -a "dest=/srv/foo/a.txt mode=600"
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$ ansible webservers -m file -a "dest=/srv/foo/b.txt mode=600 owner=mdehaan group=mdehaan"
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The ``file`` module can also create directories, similar to ``mkdir -p``::
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$ ansible webservers -m file -a "dest=/path/to/c mode=644 owner=mdehaan group=mdehaan state=directory"
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As well as delete directories (recursively) and delete files::
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$ ansible webservers -m file -a "dest=/path/to/c state=absent"
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.. _managing_packages:
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Managing Packages
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`````````````````
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There are modules available for yum and apt. Here are some examples
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with yum.
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Ensure a package is installed, but don't update it::
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$ ansible webservers -m yum -a "name=acme state=installed"
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Ensure a package is installed to a specific version::
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$ ansible webservers -m yum -a "name=acme-1.5 state=installed"
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Ensure a package is at the latest version::
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$ ansible webservers -m yum -a "name=acme state=latest"
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Ensure a package is not installed::
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$ ansible webservers -m yum -a "name=acme state=removed"
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Ansible has modules for managing packages under many platforms. If your package manager
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does not have a module available for it, you can install
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for other packages using the command module or (better!) contribute a module
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for other package managers. Stop by the mailing list for info/details.
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.. _users_and_groups:
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Users and Groups
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````````````````
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The 'user' module allows easy creation and manipulation of
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existing user accounts, as well as removal of user accounts that may
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exist::
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$ ansible all -m user -a "name=foo password=<crypted password here>"
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$ ansible all -m user -a "name=foo state=absent"
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See the :doc:`modules` section for details on all of the available options, including
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how to manipulate groups and group membership.
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.. _from_source_control:
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Deploying From Source Control
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`````````````````````````````
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Deploy your webapp straight from git::
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$ ansible webservers -m git -a "repo=git://foo.example.org/repo.git dest=/srv/myapp version=HEAD"
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Since ansible modules can notify change handlers it is possible to
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tell ansible to run specific tasks when the code is updated, such as
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deploying Perl/Python/PHP/Ruby directly from git and then restarting
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apache.
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.. _managing_services:
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Managing Services
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`````````````````
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Ensure a service is started on all webservers::
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$ ansible webservers -m service -a "name=httpd state=started"
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Alternatively, restart a service on all webservers::
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$ ansible webservers -m service -a "name=httpd state=restarted"
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Ensure a service is stopped::
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$ ansible webservers -m service -a "name=httpd state=stopped"
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.. _time_limited_background_operations:
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Time Limited Background Operations
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``````````````````````````````````
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Long running operations can be backgrounded, and their status can be
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checked on later. The same job ID is given to the same task on all
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hosts, so you won't lose track. If you kick hosts and don't want
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to poll, it looks like this::
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$ ansible all -B 3600 -a "/usr/bin/long_running_operation --do-stuff"
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If you do decide you want to check on the job status later, you can::
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$ ansible all -m async_status -a "jid=123456789"
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Polling is built-in and looks like this::
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$ ansible all -B 1800 -P 60 -a "/usr/bin/long_running_operation --do-stuff"
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The above example says "run for 30 minutes max (``-B``: 30*60=1800),
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poll for status (``-P``) every 60 seconds".
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Poll mode is smart so all jobs will be started before polling will begin on any machine.
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Be sure to use a high enough ``--forks`` value if you want to get all of your jobs started
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very quickly. After the time limit (in seconds) runs out (``-B``), the process on
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the remote nodes will be terminated.
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Typically you'll be only be backgrounding long-running
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shell commands or software upgrades only. Backgrounding the copy module does not do a background file transfer. :doc:`playbooks` also support polling, and have a simplified syntax for this.
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.. _checking_facts:
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Gathering Facts
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```````````````
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Facts are described in the playbooks section and represent discovered variables about a
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system. These can be used to implement conditional execution of tasks but also just to get ad-hoc information about your system. You can see all facts via::
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$ ansible all -m setup
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Its also possible to filter this output to just export certain facts, see the "setup" module documentation for details.
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Read more about facts at :doc:`playbooks_variables` once you're ready to read up on :doc:`playbooks`.
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.. _limiting_hosts:
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Limiting Selected Hosts
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```````````````````````
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What hosts you select to manage can be additionally constrained by using the '--limit' parameter or
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by using 'batch' (or 'range') selectors.
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As mentioned above, patterns can be strung together to select hosts in more than one group::
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$ ansible webservers:dbservers -m command -a "/bin/foo xyz"
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This is an "or" condition. If you want to further constrain the selection, use --limit, which
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also works with ``ansible-playbook``::
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$ ansible webservers:dbservers -m command -a "/bin/foo xyz" --limit region
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Assuming version 0.9 or later, as with other host patterns, values to limit can be separated with ";", ":", or ",".
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Now let's talk about range selection. Suppose you have 1000 servers in group 'datacenter', but only want to target one at a time. This is also easy::
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$ ansible webservers[0-99] -m command -a "/bin/foo xyz"
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$ ansible webservers[100-199] -m command -a "/bin/foo xyz"
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This will select the first 100, then the second 100, host entries in the webservers group. (It does not matter
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what their names or IP addresses are).
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Both of these methods can be used at the same time, and ranges can also be passed to the --limit parameter.
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.. seealso::
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:doc:`intro_configuration`
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All about the ansible config file
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:doc:`modules`
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A list of available modules
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:doc:`playbooks`
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Using ansible for configuration management & deployment
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`Mailing List <http://groups.google.com/group/ansible-project>`_
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Questions? Help? Ideas? Stop by the list on Google Groups
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`irc.freenode.net <http://irc.freenode.net>`_
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#ansible IRC chat channel
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