Re: [Userops] Why is it hard to move from one machine to another? An analysis.

[Asheesh Laroia]

Semi-sorry to be a pedant, but:

On Wed, Apr 8, 2015 at 11:04 AM, Christopher Allan Webber <address@hidden> wrote:

Dave Crossland writes:

> On 8 April 2015 at 11:22, Christopher Allan Webber <address@hidden>
> wrote:
>
>> running 80 heavy and expensive Docker images
>
>
> Huh? The entire purpose of contains is that they are light and cheap.

Are they?  Certainly compared to a VM as in terms of execution, they are
a lot smaller.  As in terms of size of the image itself, they seem to
often be just as large:

  http://stackoverflow.com/questions/24394243/why-are-docker-container-images-so-large

Astute Docker fans may point out that new images can be based off of a
lightweight image, and at that point your image is essentially a diff,
which is true!  Unfortunately, I don't think it remains that way
usually.  You need to upgrade packages on your derived image, and this
means either you need to migrate away from the base image, or maybe the
*base image* upgrades something, but regardless now you're out of sync.

If you're going to say that "Docker containers" are typically large and heavy-weight, that's a pretty reasonable thing to say!

I emphasize this because I made a Sandstorm package (aka container image) of a Python hello-world using Pyramid a few weeks ago, and the app (including all its dependencies for the container) is a 5.1MB SPK file. So I just think it's important to keep the terminology clear so that people don't think that "container" _means_ large disk footprint, but rather that "Docker container" means large disk footprint.

Also, I generally agree with everything else you said; thanks for running virtual-asheesh-laroia on your email before sending. (-;

As for reproducible images -- Sandstorm is getting there, but hasn't succeeded at that yet. It's on the queue, but we're not working on it super-duper-much at the moment.

I agree that "configuration management" via Ansible/Salt/Puppet is too much to ask non-professional-sysadmins to do.

-- Asheesh.