What?
Dock2Box is a tool that allows you to apply Docker or File images to bare-metal hardware using PXE boot.
Why?
Late vs early binding
Traditional host provisioning uses tools such as Cobbler, Kickstart and Configuration Management tools such as SaltStack, Ansible, Puppet or Chef to finalize the host configuration. This means most of the complexity is late-binding i.e. while the host is being provisioned.
By moving the complexity to the build step on a CI server, you move most of the complexity where it will fail earlier rather then later.
Obviously not everything can be early-binding, but you can keep the things that are late-binding to a minimum and thus uncover errors sooner.
Faster
At our current setup we can provision a fully configured server in less than 3 min. The main limitation is bandwidth and the size of the host image.
Idempotent (repeatable, predictable)
Since we're dealing with a host image it's much more repeatable and predictable.
Testable
One of the main issues with Configuration Management is testability: it's very hard to test since each deployment is slightly different.
With images they are basically immutable i.e. easier to test.
DevOps
DevOps is all about breaking the barriers in-between Dev and Ops. This starts by adopting the same toolchain.
In using Docker for host provisioning you can use the same toolchain for software deployment and host provisioning.
Running software on Bare-Metal
There are situations when you want to run software on bare-metal, but keep the deployment process close to what you already do with Docker. Now it's just a matter of changing your Base Image "FROM ..." in your Dockerfile and rebuild.
Workflow
Overview
Structure
| Directory | Description |
|---|---|
| base-images | Base images built using Packer and then imported into Docker |
| boot-images | Boot images used for PXE boot |
| build-images | Build image used during builds |
Default authentication
Boot image
For the boot image you can only login as "root".
Default user: root
Default password: D0ck2B0x
Base images
For the base images "root" is locked by default. You can use the following default credentials:
Default user: dock2box
Default password: D0ck2B0x
Kernel options
| Option | Type | Description |
|---|---|---|
| quiet | generic | Boot kernel in quiet mode and use progress bar |
| video | generic | Set uvesafb video mode ex. 800x600-32 |
| dma | generic | Disable DMA since it can cause issues |
| modules=module:module | generic | Load kernel modules |
| blacklist=module:module | generic | Blacklist kernel modules |
| install | generic | Install OS, this will wipe disks so do a backup first |
| sshkey=AAAAB3NzaC1y... | security | Add SSH key to "authorized_keys" for "dock2box" user |
| distro=distribution | image | Distribution being provisioned centos, fedora or ubuntu |
| image=repo/image | image | Host image name |
| tag=tag | image | Host image tag, defaults to "latest" |
| registry=registry:port | image | Docker registry, defaults to Docker Hub |
| hostname=hostname | network | Short hostname |
| ip=ip:netmask:gw | network | Static IP, defaults to DHCP |
| interface=name | network | Network interface, defaults to first interface |
| dns=dns1:dns2:search | network | DNS configuration |
| gpt | disk | Use GPT partitions |
| root_size=size | disk | size of "/root", ex. "10G" |
| var_size=size | disk | Size of "/var", ex. "15G" |
| swap_size=size | disk | Size of "swap", ex. "4G" |
Example iPXE script
#!ipxe
kernel http://my-server/dock2box/boot-images/alpine3.4.3/kernel distro=centos image=dock2box/centos7.2.1511 install gpt quiet video=800x600-32 splash
initrd http://my-server/dock2box/boot-images/alpine3.4.3/initrd
boot