在.bashrc中导出DOCKER_HOST会对终端中的同一命令产生不同的结果

Question

Before I can use my docker container (using Boot2Docker on OSX) I always have to remember to enter

export DOCKER_HOST=tcp://$(boot2docker ip 2>/dev/null):2375

in my terminal, and naturally I often forget this.

So I figured I'd just add that line to my ~/.bashrc file but when I've done this and check the value of DOCKER_HOST it's tcp://192.168.42.43:4243 instead of tcp://192.168.42.43:2375 .

Breaking it down:

• boot2docker ip => "The VM's Host only interface IP address is: 192.168.59.103"
• boot2docker ip 2 => "The VM's Host only interface IP address is: 192.168.59.103"
• boot2docker ip 2>/dev/null => "192.168.59.103" (okay I sort of get that but I have no idea how that works, and I have no idea where the :4243 is coming from."

What's actually going on here and why is the port different?

Answer 1

If you want your DOCKER_HOST environment variable to be set automatically for every terminal you open, use the "boot2docker shellinit" command. You can add this line to your .bash_profile to take care of business:

$(boot2docker shellinit)

Unfortunately, this will give you an annoying error message if your boot2docker VM is not running when you open the terminal ("error in run: VM "boot2docker-vm" is not running.") Put this in your .bash_profile instead to suppress the error message:

$(boot2docker shellinit 2>/dev/null)

More details at Github

NOTE: if you're using Docker Machine instead to manage boot2docker, the equivalent command is

eval "$(docker-machine env MACHINE-NAME)"

where MACHINE-NAME is the name of your boot2docker machine.

Answer 2

Something else is setting that environment variable for you. Why are you dumping stderr from that command to /dev/null . Is some extra info coming to stderr ?

I would do

export DOCKER_HOST="tcp://$(boot2docker ip 2>/dev/null):2375" ;
echo "Docker Host is set to ${DOCKER_HOST}"

For some debugging as it is set, then query the value at a later stage to see if something else is messing with it.

Answer 3

I think the boot2docker's socket command is more useful here, also we can simplify things a bit.

If you've not set this up before just run this in your terminal:

  echo export DOCKER_HOST=\`boot2docker socket 2\>/dev/null\` >> ~/.bashrc

If you've already been messing with this, just change your line in .bashrc to this:

  export DOCKER_HOST=`boot2docker socket 2>/dev/null`

Now to test it has worked open a new terminal and run docker run hello-world .