Ceph development environment in Docker

The Docker package is installed with

sudo apt-get install docker.io

and the loic user is made part of the docker group to allow it to run containers.

$ grep docker /etc/group

The most popular ubuntu image collection reported by

$ docker search ubuntu | head -2
NAME    DESCRIPTION                 STARS ...
ubuntu  Official Ubuntu base image  715   ...

is pulled locally with

docker pull ubuntu

A container is created from the desired image (as found by docker images) is selected with:

docker run -v /home/loic:/home/loic -t -i ubuntu:14.04

the home directory is mounted into the container because it contains the local Ceph clone used for development. The user loic is recreated in the container with

adduser loic

and the necessary development packages are installed with

apt-get build-dep ceph
apt-get install libudev-dev git-core python-virtualenv emacs24-nox ccache

The state of the container is saved for re-use with

$ docker ps
CONTAINER ID        IMAGE               ...
2c694d6d5f90        ubuntu:14.04        ...
$ docker commit 2c694d6d5f90 ubuntu-14.04-ceph-devel

Ceph is then compiled and tested locally with

cd ~/software/ceph/ceph
./configure --disable-static --with-debug \
   CC='ccache gcc' CFLAGS="-Wall -g" \
   CXX='ccache g++' CXXFLAGS="-Wall -g"
make -j4
make check

If there is not enough space in /var/lib/docker it can be moved with

$ grep ^DOCKER_OPTS /etc/default/docker
$ restart docker

The devicemapper storage backend is preferred.

$ grep ^DOCKER_OPTS /etc/default/docker
DOCKER_OPTS="-g=/home/docker --storage-driver=devicemapper"
$ restart docker

By default it uses files but Yann Dupont found that it can also be mapped to block devices instead with

--storage-opt dm.metadatadev=/dev/dm-26
--storage-opt dm.datadev=/dev/dm-27
--storage-opt dm.fs=xfs

to save I/O.

2 Replies to “Ceph development environment in Docker”

  1. Quick note :

    Not sure it save I/O but at least on my modest computer it’s definitively faster.

    /dev/dm-26 & /dev/dm-27 are local to my machine. I should have prefered using /dev/myvg/dockerdata and /dev/myvg/dockermetadata, but it’s not working for an unknown reason (maybe because it’s a symbolic link ? )

    Beware : using directly /dev/dm-xx is dangerous because of dynamic numbering…

    Also I found you have to respect the initial 100G & 10G size for lvm volumes (data and metadata) , or initial mkfs is not working.

    Of course, your mileage may vary…

  2. I created a github repo and followed this guide to create a Dockerfile (with a few mods). It can be found at github.com/ivotron/docker-cephdev.

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