Docker essentials – More work with images

Images – Messing with the stack
So we’ve had some time to digest what containers and images are.  Now let’s talk in a little greater detail about images and how they layer.  A key piece of docker is how the images stack.  For instance, let’s quickly build a container that has 3 user image layers in it.  Recall, images are the read-only pieces of the container so having 3 user layers implies that I have done 3 commits and any changes after that will be in the 4th read/write layer that lives in the container itself…

Note: Im using the term ‘user images’ to distinguish between base images and the ones that I create.  We’ll see in a minute that a base image can even have multiple images as part of the base.  I’m also going to use the term ‘image stack’ to refer to all of the images that are linked together to make a running image or container. 

I’ve highlighted each user image creation to break it out.  Essentially this is what happened…

-Ran the base CentOS image creating a container called stacking
-Created a file in the container called Continue reading

Docker essentials – Images and Containers

I’ll admit, I jumped into docker pretty quickly and found that I was getting a little ahead of myself.  After much googling and discussion, I’ve come to realize a couple things about docker that I think are well worth sharing.  I’m hoping to share them through a series of ‘Docker Essentials’ type posts.

NOTE: My first post was going to be about how to interact with docker on the CLI.  However, there are lots of other resources out there for that.  Namely, the really awesome docker documentation.  In addition, the CLI provides help/syntax on commands as well.  I’ll list a couple of resources that I used and try to explain along the way, but if you don’t recognize a command I’m using look it up! 

The docker user guide – http://docs.docker.com/userguide/
The docker CLI reference – https://docs.docker.com/reference/commandline/cli/
The docker guide book – https://github.com/kencochrane/docker-guidebook

Working with images and Containers
On first glance, I made some assumptions about this images and containers that proved to be wrong.  So let’s start with some basics.

Images are read-only.  That is, they can never be altered.  Containers are built using Continue reading

Getting Started with Docker

It can’t be helped.  There’s just too much cool stuff out there and not enough time to spend dedicating myself to one piece of technology.  That being said, I fully intend on continuing the Chef posts, but Im going to be mixing in some docker posts as well.  Im hoping that there’s some cross-connect as well where we can talk about using docker in conjunction with Chef as well.

Docker is something that I haven’t seen before.  From what I have seen so far, it appears to be an incredibly easy way to containerize applications and software on a linux system.  The docker website summarizes docker as..

“An open platform for distributed applications for developers and sysadmins.”

That summarizes things nicely, but again, why is a network guy interested in this?  First off, I’m a little tired of VMware.  Don’t confuse me being tired with a general dislike of the product.  I’ve been using VMware for years and for the most part, it works well and provides the functions I need.  On the flip side, Im not convinced there’s anything particularly special about VMware.

I’ve been using ProxMox at home for some time and it does everything that I Continue reading

Starting with Chef

You might be asking yourself why a network engineer would be concerning himself with a product like Chef.  It’s a long story, but lets start by saying that my interest was first peaked when I heard that the new line of Cisco Nexus switches would have a integrated Chef client.  I’ve known about Chef and Puppet for a long time, but I’ve never really sat down and looked to see how they worked.  So rather than starting with Chef on Nexus, I thought it would be prudent to get some base experience with the application in a more ‘normal’ application.

So how does this fit into networking?  I think we can all agree that data center networking can change.  I’m carefully phrasing that statement by using the word ‘can’.  If you don’t know it already, I don’t buy the ‘SDN will change everything you do’ line of thinking.  In fact, I try as hard as I can not even to use the term SDN.  Why?  Because it’s far too vague of a term that can mean almost anything depending on you how you want to interpret it.  Beyond being a Continue reading