<h2>Parallelism and Shell Commands<aclass="headerlink"href="#parallelism-and-shell-commands"title="Permalink to this headline">¶</a></h2>
<p>Let’s use ansible’s command line tool to reboot all web servers in Atlanta, 10 at a time:</p>
<p>Let’s use ansible’s command line tool to reboot all web servers in Atlanta, 10 at a time. First, let’s
set up SSH-agent so it can remember our credentials:</p>
<divclass="highlight-python"><pre>ssh-agent bash
ssh-add ~/.ssh/id_rsa.pub
ansible atlanta -a "/sbin/reboot" -f 10</pre>
</div>
<p>The -f 10 specifies the usage of 10 simultaneous processes.</p>
<divclass="admonition note">
<pclass="first admonition-title">Note</p>
<pclass="last">-m does not always have to be specified to /usr/bin/ansible because ‘command’ is the default ansible module</p>
</div>
<p>If we want to execute a module using the shell, we can avoid using absolute paths, and can also include
pipe and redirection operators. Read more about the differences on the <aclass="reference internal"href="modules.html"><em>Ansible Modules</em></a> page. The shell
ssh-add ~/.ssh/id_rsa.pub</pre>
</div>
<p>Now to run the command on all servers in a group, in this case, ‘atlanta’:</p>
<divclass="highlight-python"><pre>ansible atlanta -a "/sbin/reboot" -f 10</pre>
</div>
<p>If you didn’t read about patterns and groups yet, go back and read <aclass="reference internal"href="patterns.html"><em>The Inventory File, Patterns, and Groups</em></a>.</p>
<p>The -f 10 in the above specifies the usage of 10 simultaneous processes. Normally commands also take
a <cite>-m</cite> for module name, but the default module name is ‘command’, so we didn’t need to specify that
here. We’ll use <cite>-m</cite> later to run some other <aclass="reference internal"href="modules.html"><em>Ansible Modules</em></a>.</p>
<p>The command module requires absolute paths and does not support shell variables. If we want to
execute a module using the shell, we can do those things, and also use pipe and redirection operators.
Read more about the differences on the <aclass="reference internal"href="modules.html"><em>Ansible Modules</em></a> page. The shell
module looks like this:</p>
<divclass="highlight-python"><pre>ansible raleigh -m shell -a "echo \\$TERM"</pre>
</div>
<divclass="admonition note">
<pclass="first admonition-title">Note</p>
<pclass="last">When using ansible to run commands, and in particular the shell module, be careful of shell quoting rules.</p>
</div>
<divclass="admonition note">
<pclass="first admonition-title">Note</p>
<pclass="last">Note that other than the command <aclass="reference internal"href="modules.html"><em>Ansible Modules</em></a>, ansible modules usually do
not work like simple scripts. They make the remote system look like
you state, and run the commands necessary to get it there. This
is commonly referred to as ‘idempotence’, and is a core design goal of ansible. However, we also
recognize that running ad-hoc commands is equally imporant, so Ansible easily supports both.</p>
</div>
<p>When running any command with the ansible “ad hoc” CLI (as opposed to playbooks), pay particular attention
to shell quoting rules, so the shell doesn’t eat a variable before it gets passed to Ansible.</p>
<p>So far we’ve been demoing simple command execution, but most ansible modules usually do not work like
simple scripts. They make the remote system look like you state, and run the commands necessary to
get it there. This is commonly referred to as ‘idempotence’, and is a core design goal of ansible.
However, we also recognize that running ad-hoc commands is equally imporant, so Ansible easily supports both.</p>
</div>
<divclass="section"id="file-transfer-templating">
<h2>File Transfer & Templating<aclass="headerlink"href="#file-transfer-templating"title="Permalink to this headline">¶</a></h2>
<p>Here’s another use case for the <cite>/usr/bin/ansible</cite> command line.</p>
<p>Ansible can SCP lots of files to multiple machines in parallel, and
optionally use them as template sources.</p>
<p>To just transfer a file directly to many different servers:</p>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<htmlxmlns="http://www.w3.org/1999/xhtml"><head><metahttp-equiv="Content-Type"content="text/html; charset=UTF-8"/><title>ansible-playbook</title><linkrel="stylesheet"href="./docbook-xsl.css"type="text/css"/><metaname="generator"content="DocBook XSL Stylesheets V1.75.2"/></head><body><divxml:lang="en"class="refentry"title="ansible-playbook"lang="en"><aid="id554898"></a><divclass="titlepage"></div><divclass="refnamediv"><h2>Name</h2><p>ansible-playbook — run an ansible playbook</p></div><divclass="refsynopsisdiv"title="Synopsis"><aid="_synopsis"></a><h2>Synopsis</h2><p>ansible-playbook <filename.yml> … [options]</p></div><divclass="refsect1"title="DESCRIPTION"><aid="_description"></a><h2>DESCRIPTION</h2><p><spanclass="strong"><strong>Ansible playbooks</strong></span> are a configuration and multinode deployment system. Ansible-playbook is the tool
<htmlxmlns="http://www.w3.org/1999/xhtml"><head><metahttp-equiv="Content-Type"content="text/html; charset=UTF-8"/><title>ansible-playbook</title><linkrel="stylesheet"href="./docbook-xsl.css"type="text/css"/><metaname="generator"content="DocBook XSL Stylesheets V1.75.2"/></head><body><divxml:lang="en"class="refentry"title="ansible-playbook"lang="en"><aid="id330881"></a><divclass="titlepage"></div><divclass="refnamediv"><h2>Name</h2><p>ansible-playbook — run an ansible playbook</p></div><divclass="refsynopsisdiv"title="Synopsis"><aid="_synopsis"></a><h2>Synopsis</h2><p>ansible-playbook <filename.yml> … [options]</p></div><divclass="refsect1"title="DESCRIPTION"><aid="_description"></a><h2>DESCRIPTION</h2><p><spanclass="strong"><strong>Ansible playbooks</strong></span> are a configuration and multinode deployment system. Ansible-playbook is the tool
used to run them. See the project home page (link below) for more information.</p></div><divclass="refsect1"title="ARGUMENTS"><aid="_arguments"></a><h2>ARGUMENTS</h2><divclass="variablelist"><dl><dt><spanclass="term">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<htmlxmlns="http://www.w3.org/1999/xhtml"><head><metahttp-equiv="Content-Type"content="text/html; charset=UTF-8"/><title>ansible</title><linkrel="stylesheet"href="./docbook-xsl.css"type="text/css"/><metaname="generator"content="DocBook XSL Stylesheets V1.75.2"/></head><body><divxml:lang="en"class="refentry"title="ansible"lang="en"><aid="id575958"></a><divclass="titlepage"></div><divclass="refnamediv"><h2>Name</h2><p>ansible — run a command somewhere else</p></div><divclass="refsynopsisdiv"title="Synopsis"><aid="_synopsis"></a><h2>Synopsis</h2><p>ansible <host-pattern> [-f forks] [-m module_name] [-a args]</p></div><divclass="refsect1"title="DESCRIPTION"><aid="_description"></a><h2>DESCRIPTION</h2><p><spanclass="strong"><strong>Ansible</strong></span> is an extra-simple tool/framework/API for doing 'remote things' over
<htmlxmlns="http://www.w3.org/1999/xhtml"><head><metahttp-equiv="Content-Type"content="text/html; charset=UTF-8"/><title>ansible</title><linkrel="stylesheet"href="./docbook-xsl.css"type="text/css"/><metaname="generator"content="DocBook XSL Stylesheets V1.75.2"/></head><body><divxml:lang="en"class="refentry"title="ansible"lang="en"><aid="id372046"></a><divclass="titlepage"></div><divclass="refnamediv"><h2>Name</h2><p>ansible — run a command somewhere else</p></div><divclass="refsynopsisdiv"title="Synopsis"><aid="_synopsis"></a><h2>Synopsis</h2><p>ansible <host-pattern> [-f forks] [-m module_name] [-a args]</p></div><divclass="refsect1"title="DESCRIPTION"><aid="_description"></a><h2>DESCRIPTION</h2><p><spanclass="strong"><strong>Ansible</strong></span> is an extra-simple tool/framework/API for doing 'remote things' over
Michael DeHaan
13 years ago