Running Kubernetes in Offline Mode

Here I'll talk about how to run kubernetes on a flight that doesn't have wifi... or, Red Hat Summit hands on lab that is completely disconnected.  In either case, to set some context, this is useful for me while I'm running on a single host kubernetes configuration for a lab or development where network access is limited or non-existent.

The issue is that K8s tries to pull the pause container whenever it launches a pod.  As such, it tries to connect to gcr.io and make a connection to download the pause image. The gcr.io is the Google Container Registry.  When you are in a disconnected environment this will cause the pod to enter a state of pending until it can pull down the pause container. 

Here's what you can do to bypass that - at least the only thing I know you can do: pull the pause container ahead of time.  It helps if you know you'll be in an environment with limited access ahead of time. 

       
# docker pull gcr.io/google_containers/pause
Trying to pull repository gcr.io/google_containers/pause ...
6c4579af347b: Download complete 
511136ea3c5a: Download complete 
e244e638e26e: Download complete 
Status: Downloaded newer image for gcr.io/google_containers/pause:latest




# docker images
REPOSITORY                       TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
fedora/apache                    latest              1eff270e703a        7 days ago          649.7 MB
gcr.io/google_containers/pause   1.0                 6c4579af347b        11 months ago       239.8 kB
gcr.io/google_containers/pause   go                  6c4579af347b        11 months ago       239.8 kB
gcr.io/google_containers/pause   latest              6c4579af347b        11 months ago       239.8 kB

Extending Storage on an Fedora Atomic Host

I had to spend some time understanding how to use docker-storage-setup on an Atomic host. The tool docker-storage-setup comes by default and makes the configuration of storage on your Atomic host easier. I didn't read any of the provided documentation (although that probably would have helped) other than the script itself.  So, pardon me if this is a duplicate of other info out there.  It was a great way to learn more about it.  The goal here is to add more disk space to an Atomic host.  By default, the cloud image that you download has one device (vda) that is 6GB in size.  When I'm testing many, many docker builds and iterating through the Fedora-Dockerfiles repo, that's just not enough space.  So, I need to know how to expand it.

To provide some context about my environment, I'm using a local KVM environment to hack around in.  The first thing I'll do is go ahead and add a few extra disks to my environment so I can do some testing of docker-storage-setup.  Here is what we will be modifying on our running Atomic VM:

My VM is called: atomic1
New disk 1: vdb (logical name presented to VM)
New disk 2: vdc (logical name presented to VM)
New disk 3: vdd (logical name presented to VM)

As with anything you do regarding storage, make sure you have a backup.

Here is what it looks like on the Atomic VM before I add my disks:

       

# atomic host status
  TIMESTAMP (UTC)         VERSION   ID             OSNAME            REFSPEC                                                
* 2015-06-27 20:22:47     22.50     0eca6e0777     fedora-atomic     fedora-atomic:fedora-atomic/f22/x86_64/docker-host     
  2015-05-21 19:01:46     22.17     06a63ecfcf     fedora-atomic     fedora-atomic:fedora-atomic/f22/x86_64/docker-host     


# fdisk -l | grep vd
Disk /dev/vda: 6 GiB, 6442450944 bytes, 12582912 sectors
/dev/vda1  *      2048   616447   614400  300M 83 Linux
/dev/vda2       616448 12582911 11966464  5.7G 8e Linux LVM