How to make Ansible execute a shell script if a package is not installed

Question

How can I make Ansible execute a shell script if a (rpm) package is not installed? Is it somehow possible to leverage the yum module?

Answer 1

I don't think the yum module would help in this case. It currently has 3 states: absent, present, and latest. Since it sounds like you don't want to actually install or remove the package (at least at this point) then you would need to do this in two manual steps. The first task would check to see if the package exists, then the second task would invoke a command based on the output of the first command.

If you use "rpm -q" to check if a package exists then the output would look like this for a package that exists:

# rpm -q httpd
httpd-2.2.15-15.el6.centos.1.x86_64

and like this if the package doesn't exist:

# rpm -q httpdfoo
package httpdfoo is not installed

So your ansible tasks would look something like this:

- name: Check if foo.rpm is installed
  command: rpm -q foo.rpm
  register: rpm_check

- name: Execute script if foo.rpm is not installed
  command: somescript
  when: rpm_check.stdout.find('is not installed') != -1

The rpm command will also exit with a 0 if the package exists, or a 1 if the package isn't found, so another possibility is to use:

when: rpm_check.rc == 1