Difference between revisions of "Docker inside CT"
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* Kernel 042stab105.4 or later version | * Kernel 042stab105.4 or later version | ||
* Kernel module veth module is loaded on host | * Kernel module veth module is loaded on host | ||
+ | * If node have no bridge on host - please to do not forget to load bridge module on host too | ||
== Container tuning == | == Container tuning == |
Revision as of 10:51, 17 February 2015
Since OpenVZ kernel 042stab105.4 it is possible to run Docker inside containers. This article describes how.
Contents
Prerequisites
- Kernel 042stab105.4 or later version
- Kernel module veth module is loaded on host
- If node have no bridge on host - please to do not forget to load bridge module on host too
Container tuning
- Create Fedora 20 container:
vzctl create $veid --ostemplate fedora-20-x86_64
- Turn on bridge feature to allow docker creating bridged network:
vzctl set $veid --features bridge:on --save
- Setup Container veth-based network:
vzctl set $veid --netif_add eth0 --save
- Allow all iptables modules to be used in containers:
vzctl set $veid --netfilter full --save
- Configure custom cgroups in systemd:
- systemd reads /proc/cgroups and mounts all cgroups enabled there, though it doesn't know there's a restriction that only freezer,devices and cpuacct,cpu,cpuset can be mounted in container, but not freezer, cpu etc. separately
vzctl mount $veid echo "JoinControllers=cpu,cpuacct,cpuset freezer,devices" >> /vz/root/$veid/etc/systemd/system.conf
- Start the container:
vzctl start $veid
Prepare Docker in container
These steps are to be performed inside the container.
- Install Docker:
yum -y install docker-io
- Start docker daemon
docker -d -s vfs
Example usage
Wordpress
Use Docker to start Wordpress (official, standard way).
- Start mysql docker:
docker run --name test-mysql -e MYSQL_ROOT_PASSWORD=123 -d mysql
- Start wordpress:
docker run --name test-wordpress --link test-mysql:mysql -p 8080:80 -d wordpress
- Access wordpress server by container IP and port 8080:
http://container_ip:8080
Limitations
- This feature is currently in beta
- Only "vfs" Docker graph driver is currently supported
- Checkpointing and live migration of a container with Docker containers inside is not supported