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WORKAROUNDS.md

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Workarounds

Note: The following steps are meant as a temporary solution and won't be needed anymore in the future.

Port forwarding

Let's say your Docker container exposes the port 8000 and you want access it from your other computers on your LAN. You can do it temporarily, using ssh:

Run following command (and keep it open):

$ boot2docker ssh -vnNTL 8000:localhost:8000

or you can set up a permanent VirtualBox NAT Port forwarding:

$ VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port8000,tcp,,8000,,8000";

If the vm is already running, you should run this other command:

$ VBoxManage controlvm "boot2docker-vm" natpf1 "tcp-port8000,tcp,,8000,,8000";

Now you can access your container from your host machine under localhost:8000.

Port forwarding on steroids

If you use a lot of containers which expose the same port, you have to use docker dynamic port forwarding.

For example, running 3 nginx containers:

  • container-1 : 80 -> 49153 (i.e. docker run -p 49153:80 ...)
  • container-2 : 80 -> 49154 (i.e. docker run -p 49154:80 ...)
  • container-3 : 80 -> 49155 (i.e. docker run -p 49155:80 ...)

By using the VBoxManage modifyvm command of VirtualBox you can forward all 49XXX ports to your host. This way you can easily access all 3 webservers in you browser, without any ssh localforwarding hack. Here's how it looks like:

# vm must be powered off
for i in {49000..49900}; do
 VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port$i,tcp,,$i,,$i";
 VBoxManage modifyvm "boot2docker-vm" --natpf1 "udp-port$i,udp,,$i,,$i";
done

This makes container-1 accessible at localhost:49153, and so on.

In order to reverse this change, you can do:

# vm must be powered off
for i in {49000..49900}; do
 VBoxManage modifyvm "boot2docker-vm" --natpf1 delete "tcp-port$i";
 VBoxManage modifyvm "boot2docker-vm" --natpf1 delete "udp-port$i";
done

BTRFS (ie, mkfs inside a privileged container)

Note: AUFS on top of BTRFS has many, many issues, so the Docker engine's init script will autodetect that /var/lib/docker is a btrfs partition and will set -s btrfs for you.

docker@boot2docker:~$ docker pull debian:latest
Pulling repository debian
...
docker@boot2docker:~$ docker run -i -t --rm --privileged -v /dev:/hostdev debian bash
root@5c3507fcae63:/# fdisk /hostdev/sda # if you need to partition your disk
Command: o
Command: n
Select: p
Partition: <enter>
First sector: <enter>
Last sector: <enter>
Command: w
root@5c3507fcae63:/# apt-get update && apt-get install btrfs-tools
...
The following NEW package will be installed:
  btrfs-tools
...
Setting up btrfs-tools (...) ...
root@5c3507fcae63:/# mkfs.btrfs -L boot2docker-data /hostdev/sda1
...
fs created label boot2docker-data on /hostdev/sda1
...
root@5c3507fcae63:/# exit
docker@boot2docker:~$ sudo reboot