How can I get Docker Linux container information from within the container itself?

I would like to make my docker containers aware of their configuration, the same way you can get information about EC2 instances through metadata.

I can use (provided docker is listening on port 4243)

curl http://172.17.42.1:4243/containers/$HOSTNAME/json

to get some of its data, but would like to know if there is a better way at least the get the full ID of the container, because HOSTNAME is actually shortened to 12 characters and docker seems to perform a "best match" on it.

Also, how can I get the external IP of the docker host (other than accessing the EC2 metadata, which is specific to AWS)

Solution 1:

Unless overridden, the hostname seems to be the short container id in Docker 1.12

root@d2258e6dec11:/project# cat /etc/hostname
d2258e6dec11

Externally

$ docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED                 STATUS                      PORTS               NAMES
d2258e6dec11        300518d26271        "bash"              5 minutes ago       

$ docker -v
Docker version 1.12.0, build 8eab29e, experimental

Solution 2:

I've found out that the container id can be found in /proc/self/cgroup

So you can get the id with :

cat /proc/self/cgroup | grep -o  -e "docker-.*.scope" | head -n 1 | sed "s/docker-\(.*\).scope/\\1/"