[chef] Re: Ohai and Chef...

[Brad Knowles < >]

On Sep 10, 2013, at 11:37 AM, Russell Bateman 
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 wrote:

> I'm pretty sure that what I'm doing is not what's called Chef Solo, which 
> as I understand it, is using opscode somehow in place of managing my own 
> Chef server.

Chef-solo is a mix of chef-client and chef-server, and allows you to run Chef 
recipes without needing to connect to a chef-server.  It gives you a fully 
and completely self-contained implementation of a simplified system.

> In http://docs.opscode.com/essentials_nodes_chef_run.html, I see something ;
> called Ohai, and I've heard it referenced in this group forum, read about 
> it in references in documentation here and there. I don't have 
> /etc/chef/ohai_plugins yet. Etc.
>       • What is the significance of Ohai?

Ohai is used to discover what is installed on a machine and how it is 
configured.  Puppet has a similar tool called "facter".  These kinds of tools 
can be useful in their own right, although they are a critical component of 
systems like Chef and Puppet.

See <http://docs.opscode.com/ohai.html> for more information.

>       • Is it "just there"?

It is there, but I wouldn't use the word "just" in connection with Ohai.  It 
is a vital component of Chef.

>       • Why single it out a name in the first place rather than it just 
> being "Chef"?

IIRC, it is maintained separate from the rest of the Chef codebase, in part 
so that upgrades and changes can be made to Ohai that do not require you to 
update the entire chef-client system.

>       • Is it something that wasn't there originally?
>       • If I'm not explicitly listing it as a cookbook/recipe in my runs, 
> am I nevertheless using it anyway?

Running Ohai is the first thing done as part of a chef-client or chef-solo 
run, so there is no escaping it.  Like it or not, if you're using chef-client 
or chef-solo, then you're using Ohai.  Consider yourself lucky, because Ohai 
ends up having to do some pretty whacky and wild things in order to get all 
the information it does.

> Thanks for any comments--I'm still as green as they come at this Chef stuff.

Generally speaking, most questions you have are likely to be answered in the 
Chef documentation.  Your first stop for information should be at 
<http://docs.opscode.com/>, and don't forget the search interface at 
<http://docs.opscode.com/search.html> if you don't find any obvious links 
from that main page.

--
Brad Knowles 
<
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LinkedIn Profile: <http://tinyurl.com/y8kpxu>