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Connection Issues

There are currently a few connections issues in Boot2docker. If you see

Couldn't connect to Docker daemon

or something like

FATA[0000] An error occurred trying to connect: Get x509: certificate is valid for,, not

it could be one of many issues reported recently. Try this

boot2docker ssh sudo /etc/init.d/docker restart

and run docker ps to see if you can connect. If not, then try deleting the keys

boot2docker ssh sudo rm /var/lib/boot2docker/tls/server*.pem
boot2docker ssh sudo /etc/init.d/docker restart
boot2docker shellinit

and run docker ps to see if you can connect. If that doesn't work:

  • boot2docker restart
  • docker ps # Should see some output, not errors.

Port forwarding

Note: these instructions are for TCP only, not UDP. If you need to port forward UDP packets, the commands are similar. Please see the VirtualBox NAT documentation for more details.

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) to use ssh to forward all accesses to your OSX/Windows box's port 8000 to the Boot2Docker virtual machine's port 8000:

$ 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";

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";

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:
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