Tuesday Dec 03, 2013

Oracle Linux 6.5 and Docker

I have been following the Docker project with great interest for a little while now but never got to actually try it out at all. I found a little bit of time tonight to at least try hello world.

Since docker relies on cgroups and lxc, it should be easy with uek3. We provide official support for lxc, we are in fact a big contributor to the lxc project (shout out to Dwight Engen) and the docker website says that you need to be on 3.8 for it to just work. So, OL6.5 + UEK3 seems like the perfect combination to start out with.

Here are the steps to do few very simple things:

- Install Oracle Linux 6.5 (with the default UEK3 kernel (3.8.13))

- To quickly play with docker you can just use their example

(*) if you are behind a firewall, set your HTTP_PROXY

-> If you start from a Basic Oracle Linux 6.5 installation, install lxc first. Your out-of-the-box OL should be configured to access the public-yum repositories.

# yum install lxc

-> ensure you mount the cgroups fs

# mkdir -p /cgroup ; mount none -t cgroup /cgroup

-> grab the docker binary

# wget https://get.docker.io/builds/Linux/x86_64/docker-latest -O docker
# chmod 755 docker

-> start the daemon

(*) again, if you are behind a firewall, set your HTTP_PROXY setting (http_proxy won't work with docker)

# ./docker -d &
-> you can verify if it works

# ./docker version
Client version: 0.7.0
Go version (client): go1.2rc5
Git commit (client): 0d078b6
Server version: 0.7.0
Git commit (server): 0d078b6
Go version (server): go1.2rc5

-> now you can try to download an example using ubuntu (we will have to get OL up there :))

# ./docker run -i -t ubuntu /bin/bash

this will go and pull in the ubuntu template and run bash inside

# ./docker run -i -t ubuntu /bin/bash
WARNING: IPv4 forwarding is disabled.
root@7ff7c2bae124:/# 

and now I have a shell inside ubuntu!

-> ok so now on to playing with OL6. Let's create and import a small OL6 image.

-> first install febootstrap so that we can create an image

# yum install febootstrap

-> now you have to point to a place where you have the repoxml file and the packages on an http server. I copied my ISO content over to a place

I will install some basic packages in the subdirectory ol6 (it will create an OL installed image - this is based on what folks did for centos so it works the same (https://github.com/dotcloud/docker/blob/master/contrib/mkimage-centos.sh)

# febootstrap -i bash -i coreutils -i tar -i bzip2 -i gzip \
-i vim-minimal -i wget -i patch -i diffutils -i iproute -i yum ol6 ol6 http://wcoekaer-srv/ol/

# touch ol6/etc/resolv.conf
# touch ol6/sbin/init

-> tar it up and import it

# tar --numeric-owner -jcpf ol6.tar.gz -C ol6 .
# cat ol6.tar.gz | ./docker import - ol6

Success!

List the image

# ./docker images

# ./docker images
REPOSITORY          TAG                 IMAGE ID      
      CREATED             SIZE
ol6                 latest              d389ed8db59d    
      8 minutes ago       322.7 MB (virtual 322.7 MB)
ubuntu              12.04               8dbd9e392a96     
      7 months ago        128 MB (virtual 128 MB)

And now I have a docker image with ol6 that I can play with!

# ./docker run -i -t ol6 ps aux
WARNING: IPv4 forwarding is disabled.
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  1.0  0.0  11264   656 ?        R+   23:58   0:00 ps aux

Way more to do but this all just worked out of the box!

# ./docker run ol6 /bin/echo hello world
WARNING: IPv4 forwarding is disabled.
hello world

That's it for now. Next time, I will try to create a mysql/ol6 image and various other things.

This really shows the power of containers on Linux and Linux itself. We have all these various Linux distributions but inside lxc (or docker) you can run ubuntu, debian, gentoo, yourowncustomcrazything and it will just run, old versions of OL, newer versions of OL, all on the same host kernel.

I can run OL6.5 and create OL4, OL5, OL6 containers or docker images but I can also run any old debian or slackware images at the same time.

About

Wim Coekaerts is the Senior Vice President of Linux and Virtualization Engineering for Oracle. He is responsible for Oracle's complete desktop to data center virtualization product line and the Oracle Linux support program.

You can follow him on Twitter at @wimcoekaerts

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