Enable Docker Remote REST API on Docker Host in Ubuntu

Introduction

Docker provides remote REST API which is beneficial if you want to connect to a remote docker host. Few of the functions which you can achieve using Docker REST API over a simple browser are

• Create and Manage Containers
• Get low-level information about a container
• Get Container Logs
• Start/Stop container
• Kill a container

Things that didn’t worked

Over the internet, most of the people have suggested editing DOCKER_OPTS variable.

• I changed DOCKER_OPTS in the /etc/default/docker file but it didn’t have any effect
• Then I tried changing DOCKER_OPTS in the file /etc/init/docker.conf but again no success.

What really worked for me to enable docker remote API on docker host

• Navigate to /lib/system/system in your terminal and open docker.service file
  
  vi /lib/systemd/system/docker.service

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  vi /lib/systemd/system/docker.service

• Find the line which starts with ExecStart and adds  -H=tcp://0.0.0.0:2375 to make it look like
  
  ExecStart=/usr/bin/docker daemon -H=fd:// -H=tcp://0.0.0.0:2375

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  ExecStart=/usr/bin/docker daemon -H=fd:// -H=tcp://0.0.0.0:2375

• Save the Modified File
• Reload the docker daemon
  
  systemctl daemon-reload

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  systemctl daemon-reload

• Restart the container
  
  sudo service docker restart

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  sudo service docker restart

• Test if it is working by using this command, if everything is fine below command should return  a JSON
  
  curl http://localhost:2375/images/json

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  curl http://localhost:2375/images/json

• To test remotely, use the PC name or IP address of Docker Host