A Random Walk Down Tech Street

I need to copy a few files into my docker container.. Should be easy right? Turns out it’s not so trivial. In Docker 1.0.0 and earlier the docker cp command can be used to copy files from a container to the host, but not the other way around…

Most of the time you can work around this by using an ADD statement in the Dockerfile but I often need to populate some data within data-only volume containers before I start other containers that use the data. To achieve copying data into the volume you can simply use tar and pipe the contents into the volume within a new container like so:\

Sometimes it can be useful to have a docker image with just the bare essentials. Maybe you want to have a container with just enough to run your app or you are using something like data volume containers and want just enough to browse the filesystem. Either way you can create your own minimalist busybox image on Fedora with a pretty simple script.

The script below was inspired a little from Marek Goldmann’s post about creating a minimal image for wildfly and a little from the busybox website .
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Introduction

I often find that my tastes for hard drive configurations on my installed systems is a bit outside of the norm. I like playing with thin LVs, BTRFS snapshots, or whatever new thing there is around the corner. The Anaconda UI has been adding support for these fringe cases but I still find it hard to get Anaconda to do what I want in certain cases.

An example of this happened most recently when I went to reformat and install Fedora 20 on my laptop. Ultimately what I wanted was encrypted root and swap devices and btrfs filesystems on root and boot. One other requirement was that I needed to leave sda4 (a Windows Partition) completely intact. At the end the configuration should look something like:
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Introduction

Some time ago I wrote a few posts ( 1, 2 ) on how to use script to record a terminal session and then scriptreplay to play it back. This functionality can be very useful by enabling you the power to show others what happens when you do insert anything here.

I have been happy with this solution for a while until one day Wolfgang Richter commented on my original post and shared a project he has been working on known as TermRecord.

I gave it a spin and have been using it quite a bit. Sharing a terminal recording now becomes much easier as you can simply email the .html file or you can host it yourself and share links. As long the people you are sharing with have a browser then they can watch the playback. Thus, it is not tied to a system with a particular piece of software and clicking a link to view is very easy to do :)

Introduction

Docker is an emerging technology that has garnered a lot of momentum in the past year. I have been busy with a move to NYC and a job change (now officially a Red Hatter), so I am just now getting around to getting my feet wet with Docker.

Last night I sat down and decided to bang out some steps for installing wordpress in a docker container. Eventually I plan to move this site into a container so I figured this would be a good first step.

Introduction

I have been running my home desktop on thin logical volumes for a while now. I have enjoyed the flexibility of this setup and I like taking a snapshot before making any big changes to my setup. Recently I decided to update to Fedora 20 from Fedora 19 and I hit some trouble along the way because the Fedora 20 initramfs (images/pxeboot/upgrade.img) that is used by fedup for the upgrade does not have support for thin logical volumes. After running fedup and rebooting you end up with a message to the screen that looks something like this:\

Introduction

I decided this year to take part in the Fedora Virtualization Test Day on October 8th. In order to take part I needed a system with Fedora 20 installed so that I could then create VMs on top. Since I like my current setup and I didn’t have a hard drive laying around that I wanted to wipe I decided to give nested virtualization a shot.

Most of the documentation I have seen for nested virtualization has come from Kashyap Chamarthy. Relevant posts are here, here, and here. He has done a great job with these tutorials and this post is nothing more than my notes for what I found to work for me.

Introduction

I have been using BTRFS snapshots for a while now on my laptop to incrementally save the state of my machine before I perform system updates or run some harebrained test. I quickly ran into a problem though, as on a smaller filesystem I was running out of space. I then wanted to be able to look at each snapshot and easily determine how much space I could recover if I deleted each snapshot. Surprisingly this information was not readily available. Of course you could determine the total size of each snapshot by using du, but that only tells you how big the entire snapshot is and not how much of the snapshot is exclusive to this snapshot only..

Enter filesystem quota and qgroups in git commit 89fe5b5f666c247aa3173745fb87c710f3a71a4a . With quota and qgroups (see an overview here ) we can now see how big each of those snapshots are, including exclusive usage.

I ran across a great PDF from this year’s Red Hat Summit in Boston. Hosted by Christoph Doerbech and Jonathan Brassow the lab covers the following topics:\

• What is LVM? What are filesystems? etc..
• Creating PVs, VGs, LVs.
• LVM Striping and Mirroring.
• LVM Raid.
• LVM Snapshots (and reverting).
• LVM Sparse Volumes (a snapshot of /dev/zero).
• LVM Thin LVs and new snapshots.

Check out the PDF here . If that link ceases to work at some point I have it hosted here as well.

Hope everyone can use this as a great learning tool!

Dusty

Introduction

Want to take advantage of the efficiency and improved snapshotting of thin LVs on an existing system? It will take a little work but it is possible. The following steps will show how to convert a CentOS 6.4 basic installation to use thin logical volumes for the root device (containing the root filesystem).

Preparation

To kick things off there are few preparation steps we need that seem a bit unreleated but will prove useful. First I enabled LVM to issue discards to underlying block devices (if you are interested in why this is needed you can check out my post here. )
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