The following examples show how to use /usr/bin/ansible for running ad-hoc tasks. Start here. For configuration management and deployments, you’ll want to pick up on using /usr/bin/ansible-playbook – the concepts port over directly.
Let’s use ansible’s command line tool to reboot all web servers in Atlanta, 10 at a time:
ssh-agent bash
ssh-add ~/.ssh/id_rsa.pub
ansible atlanta -a "/sbin/reboot" -f 10
The -f 10 specifies the usage of 10 simultaneous processes.
Note
-m does not always have to be specified to /usr/bin/ansible because ‘command’ is the default ansible module
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 Ansible Modules page. The shell module looks like this:
ansible raleigh -m shell -a "echo \\$TERM"
Note
When using ansible to run commands, and in particular the shell module, be careful of shell quoting rules.
Note
Note that other than the command Ansible Modules, 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.
Ansible can SCP lots of files to multiple machines in parallel, and optionally use them as template sources.
To just 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. If facter or ohai were installed on the remote machine, variables from those programs can be accessed too, which the appropriate prefix:
This is an Ansible variable: {{ favcolor }}
This is a facter variable: {{ facter_hostname }}
This is an ohai variable: {{ ohai_foo }}
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.
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 a module for managing packages with yum. You can install for other package manages using the command module or contribute a module for other package managers. Stop by the mailing list for info/details.
Deploy your webapp straight from git:
ansible webservers -m git -a "repo=git://foo 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.
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"
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.
See also