Command Line Examples¶

Parallelism and Shell Commands¶

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:

ssh-agent bash
ssh-add ~/.ssh/id_rsa.pub

Now to run the command on all servers in a group, in this case, ‘atlanta’:

ansible atlanta -a "/sbin/reboot" -f 10

If you want to run commands as a different user than root:

ansible atlanta -a "/usr/bin/foo" -u yourname

If you want to run commands through sudo:

ansible atlanta -a "/usr/bin/foo" -u yourname --sudo [--ask-sudo-pass]

Use –ask-sudo-pass (-K) if you are not using passwordless sudo.

Ok, so those are basics. If you didn’t read about patterns and groups yet, go back and read The Inventory File, Patterns, and Groups.

The -f 10 in the above specifies the usage of 10 simultaneous processes. Normally commands also take a -m for module name, but the default module name is ‘command’, so we didn’t need to specify that here. We’ll use -m later to run some other Ansible Modules.

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 Ansible Modules page. The shell module looks like this:

ansible raleigh -m shell -a 'echo $TERM'

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. For example, using double vs single quotes in the above example would evaluate the variable on the box you were on.

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 important, so Ansible easily supports both.

File Transfer & Templating¶

Here’s another use case for the /usr/bin/ansible command line.

Ansible can SCP lots of files to multiple machines in parallel, and optionally use them as template sources.

To transfer a file directly to many different servers:

ansible atlanta -m copy -a "src=/etc/hosts dest=/tmp/hosts"

To use templating, first run the setup module to put the template variables you would like to use on the remote host. Then use the template module to write the files using those templates.

Templates are written in Jinja2 format. Playbooks (covered elsewhere in the documentation) will run the setup module for you, making this even simpler:

ansible webservers -m setup    -a "favcolor=red ntp_server=192.168.1.1"
ansible webservers -m template -a "src=/srv/motd.j2 dest=/etc/motd"
ansible webservers -m template -a "src=/srv/ntp.j2 dest=/etc/ntp.conf"

Ansible variables are used in templates by using the name surrounded by double curly-braces. Ansible provides some ‘facts’ about the system being managed automatically in playbooks or when the setup module is run manually. If facter or ohai were installed on the remote machine, variables from those programs can be accessed too, using the appropriate prefix:

This is an Ansible variable: {{ favcolor }}
This is an Ansible fact: {{ ansible_hostname }}
This is a facter fact: {{ facter_hostname }}
This is an ohai fact: {{ ohai_foo }}

Using the Ansible facts is generally preferred as that way you can avoid a dependency on ruby. If you want to use facter instead, you will also need rubygem-json because the facter packages may forget this as a dependency.

The file module allows changing ownership and permissions on files. These same options can be passed directly to the copy or template modules as well:

ansible webservers -m file -a "dest=/srv/foo/a.txt mode=600"
ansible webservers -m file -a "dest=/srv/foo/b.txt mode=600 owner=mdehaan group=mdehaan"

The file module can also create directories, similar to mkdir -p:

ansible webservers -m file -a "dest=/path/to/c mode=644 owner=mdehaan group=mdehaan state=directory"

As well as delete directories (recursively) and delete files:

ansible webservers -m file -a "dest=/path/to/c state=absent"

The mode, owner, and group arguments can also be used on the copy or template lines.

Managing Packages¶

There are modules available for yum and apt. Here are some examples with yum.

Ensure a package is installed, but don’t update it:

ansible webservers -m yum -a "pkg=acme state=installed"

Ensure a package is installed to a specific version:

ansible-webservers -m yum -a "pkg=acme-1.5 state=installed"

Ensure a package is at the latest version:

ansible webservers -m yum -a "pkg=acme state=latest"

Ensure a package is not installed:

ansible-webservers -m yum -a "pkg=acme state=removed"

Currently Ansible only has modules for managing packages with yum and apt. You can install for other packages for now using the command module or (better!) contribute a module for other package managers. Stop by the mailing list for info/details.

Users and Groups¶

The user module allows easy creation and manipulation of existing user accounts, as well as removal of user accounts that may exist:

ansible all -m user -a "name=foo password=<crypted password here>"

ansible all -m user -a "name=foo state=absent"

See the Ansible Modules section for details on all of the available options, including how to manipulate groups and group membership.

Deploying From Source Control¶

Deploy your webapp straight from git:

ansible webservers -m git -a "repo=git://foo.example.org/repo.git dest=/srv/myapp version=HEAD"

Since ansible modules can notify change handlers (see Playbooks) it is possible to tell ansible to run specific tasks when the code is updated, such as deploying Perl/Python/PHP/Ruby directly from git and then restarting apache.

Managing Services¶

Ensure a service is started on all webservers:

ansible webservers -m service -a "name=httpd state=started"

Alternatively, restart a service on all webservers:

ansible webservers -m service -a "name=httpd state=restarted"

Ensure a service is stopped:

ansible webservers -m service -a "name=httpd state=stopped"

Time Limited Background Operations¶

Long running operations can be backgrounded, and their status can be checked on later. The same job ID is given to the same task on all hosts, so you won’t lose track. If you kick hosts and don’t want to poll, it looks like this:

ansible all -B 3600 -a "/usr/bin/long_running_operation --do-stuff"

If you do decide you want to check on the job status later, you can:

ansible all -m async_status -a "jid=123456789"

Polling is built-in and looks like this:

ansible all -B 3600 -P 60 -a "/usr/bin/long_running_operation --do-stuff"

The above example says “run for 60 minutes max (60*60=3600), poll for status every 60 seconds”.

Poll mode is smart so all jobs will be started before polling will begin on any machine. Be sure to use a high enough –forks value if you want to get all of your jobs started very quickly. After the time limit (in seconds) runs out (-B), the process on the remote nodes will be terminated.

Any module other than copy or template can be backgrounded. Typically you’ll be backgrounding long-running shell commands or software upgrades only. Playbooks also support polling, and have a simplified syntax for this.