Following the tutorial and tool setup as outlined here; https://hyperledger.github.io/composer/installing/development-tools.html
On the very last step, I executed the script to download and install local Fabric runtime:
cd ~/fabric-tools
./downloadFabric.sh
The resulting log in the console contained this error at the very end:
# Pull and tag the latest Hyperledger Fabric base image.
docker pull hyperledger/fabric-peer:$ARCH-1.0.4
Warning: failed to get default registry endpoint from daemon (Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.35/info: dial unix /var/run/docker.sock: connect: permission denied). Using system default: https://index.docker.io/v1/
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.35/images/create?fromImage=hyperledger%2Ffabric-peer&tag=x86_64-1.0.4: dial unix /var/run/docker.sock: connect: permission denied
What should I do about this warning?
I think this answer might be the reason behind it. The shell keeps your session stored. SO, in order to get the updates working, you have to close the shell and restart it again. That's why it worked after the restart. Please correct me if I'm wrong!
So your issue is a Docker issue - not a Hyperledger Composer issue FYI. I think this may help you https://techoverflow.net/2017/03/01/solving-docker-permission-denied-while-trying-to-connect-to-the-docker-daemon-socket/
Possibly a docker install issue - didn't install correctly? See here https://superuser.com/questions/835696/how-solve-permission-problems-for-docker-in-ubuntu where it talks about being in the docker group. Or else you can find an answer on Google.