Freeing up a Volume from a Nova server that errored

Trial and error. Its a key part of getting work done in my field, and I make my share of errors. Today, I tried to create a virtual machine in Nova using a bad glance image that I had converted to a bootable volume:

The error message was:

 {u'message': u'Build of instance d64fdd07-748c-4e27-b212-59e8cef9d6bf aborted: Block Device Mapping is Invalid.', u'code': 500, u'created': u'2018-01-31T03:10:56Z'}

The VM could not release the volume.

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Creating an Ansible Inventory file using Jinja templating

While there are lots of tools in Ansible for generating an inventory file dynamically, in a system like this, you might want to be able to perform additional operations against the same cluster. For example, once the cluster has been running for a few months, you might want to do a Yum update. Eventually, you want to de-provision. Thus, having a remote record of what machines make up a particular cluster can be very useful. Dynamic inventories can be OK, but often it takes time to regenerate the inventory, and that may slow down an already long process, especially during iterated development.

So, I like to generate inventory files. These are fairly simple files, but they are not one of the supported file types in Ansible. Ansible does support ini files, but the inventory files have maybe lines that are not in key=value format.

Instead, I use Jinja formatting to generate inventory files, and they are pretty simple to work with.

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Getting Shade for the Ansible OpenStack modules

When Monty Taylor and company looked to update the Ansible support for OpenStack, they realized that there was a neat little library waiting to emerge: Shade. Pulling the duplicated code into Shade brought along all of the benefits that a good refactoring can accomplish: fewer cut and paste errors, common things work in common ways, and so on. However, this means that the OpenStack modules are now dependent on a remote library being installed on the managed system. And we do not yet package Shade as part of OSP or the Ansible products. If you do want to use the OpenStack modules for Ansible, here is the “closest to supported” way you can do so.

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Picking the Right Hammer for the Job

Red Hat Satellite Server is a key tool in the provisioning process for the systems in our Labs.  In one of our labs we have an older deployment running Satellite 6 which maps to the upstream project The Foreman version 1.11.  Since I want to be able to perform repeatable operations on this server, I need to make Web API calls.

The easiest way to do this is to use the Hammer CLI. But it turns out the version of Hammer is somewhat tied to the version of Satellite server; the version I have in Fedora 27 Does not talk to this older Satellite instance.  So, I want to run an older Hammer.

I decided to use this as an opportunity to walk through running an RPM managed application targetted for RHEL 6/EPEL 6 via Docker.

Edit: actually, this might not be the case, but the rest of the learning process was interesting enough that I kept working at it.
Edit2: This was necessary, see the bottom. Also, the 1.11 in the URL refers to the upstream repo for theforeman. I’d use a different repo for building using supported RH RPMs.

Here is what I learned.

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Docker without sudo on Centos 7

I have been geting prepped to build the OpenShift origin codebase on Centos 7.  I started from a fairly minimal VM which did not have docker or Development Tools installed.  Once I thought I had all the prerequisites, I kicked off the build and got

Cannot connect to the Docker daemon. Is the docker daemon running on this host?

This seems to be due to the fact that  the ayoung user does not have permissions to read/write on the domain socket.  /var/run/docker.sock

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