Not a traditional REDtalks post today (no interview/demo), but this took me a while to work out so I thought I’d share.
What’s this about?
It all started with me building REST extensibility solutions for F5 Networks in AWS. I created (Launched) a new AWS AMI Linux instance – yep, the very first one on the list: “Amazon Linux AMI 2017.03.0 (HVM), SSD Volume Type“.
Next, I followed the AWS instructions to install docker:
sudo yum update -y
sudo yum install -y docker
sudo service docker start
sudo usermod -a -G docker ec2-user
docker info
NOTE: Full docs here: http://docs.aws.amazon.com/AmazonECS/latest/developerguide/docker-basics.html
This is where I got stuck!
As part of the solution I needed to issue a docker command on the docker host, from inside a container… Ok, Batman, to the Google-copter…
There’s loads of suggestions out there to map /var/run/docker.sock into the container using -v. For example:
$ docker run -it -v /var/run/docker.sock:/var/run/docker.sock my_container sh
With this you can execute:
$ curl --unix-socket /var/run/docker.sock http:/containers/json
HOWEVER, there are loads of forum posts saying to be real careful about mapping /var/run/docker.sock to all you containers…
What to do?
Enable the API over TCP!
Back to the Google-copter, there are a few posts out there about getting it running on Ubuntu but none for the Linux AMI distro…
A solution (hours later…)
1. Change some startup options:
The default ‘OPTIONS’ in /etc/init.d/docker is:
OPTIONS="${OPTIONS:-${other_args}}"
we need to change this to:
OPTIONS="${OPTIONS:-${other_args}} -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock"
So, you need to go ahead and edit that to something link this:
$ sudo vi /etc/init.d/docker
#OPTIONS="${OPTIONS:-${other_args}}"
OPTIONS="${OPTIONS:-${other_args}} -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock"
2. Restart docker for these options to take effect:
sudo service docker restart
Now you have enabled the docker API over TCP! #w00t
Test the API
Lets get the API version:
curl http://<ip_address>:2375/version
NOTE: Replace <ip_address> with the IP address of the docker host, or its hostname!
The response will look something like this:
{"Version":"1.12.6","ApiVersion":"1.24","GitCommit":"7392c3b/1.12.6","GoVersion":"go1.6.3","Os":"linux","Arch":"amd64","KernelVersion":"4.9.20-11.31.amzn1.x86_64","BuildTime":"2017-03-07T20:34:04.601909006+00:00"}
Note the:
"ApiVersion":"1.24"
Now add that version number to the beginning of the URI, slap json on the end of it, and presto:
curl http://<ip_address>:2375/v1.24/images/json
Returns:
[{"Id":"sha256:80ee3a0f225e543668eca9922bf5642bce0e484403df665f3ac9b107d2895d40","ParentId":"","RepoTags":["npearce/ilxe-festivus:latest"],"RepoDigests":["npearce/ilxe-festivus@sha256:973dbf813f6a7f07929b8fd86da4fa9b79f613228e3942fb35d9d525fcfa61b0"],"Created":1495771390,"Size":85001082,"VirtualSize":85001082,"Labels":{}}]
Now you can go read this: https://docs.docker.com/engine/api/v1.24/
Enjoy!
CAUTION: One last step, and this is REALLY important! Don’t leave your Docker API open on the Internet!
