Dockers

Dockers 101 – Series 4 of N – Using Docker-Setting Up a Redis Container

Requirement: Lets imagine that as a DevOps, you have been asked to create a container to run redis, and try different docker commands to run redis in foreground, […]

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Mohd Naeem
  • Requirement:
    • Lets imagine that as a DevOps, you have been asked to create a container to run redis, and try different docker commands to run redis in foreground, background, with specific port binding, with dynamic port binding, persisting data and logs from container to a volume on host
  • Strategy:
    • search the name of image on docker hub
    • run the redis container in background as its a database and will take time to setup
    • run redis in background
    • run redis with specific port
    • run redis with dynamic port
    • run redis with volume persistance
  • Solution:
    • Login to your Host machine(in my case a CentOS 7 machine)
    • Make a directory “TicTackToe” and go to the directory – mkdir myredis && cd myredis
    • How to
      • search for an image – docker search <image-name>
      • e.g. docker search redis
      • Capture
      • run an image
        • in interactive mode  – docker run -it <image-name>
          • docker run -it redis
          • switch  “-it” is for interactive mode
        • in background mode – docker run -d <image-name>
          • docker run -d redis
          • switch  “-d” is for background mode
      • check if container is running – docker container ls or docker ps -a
      • Capture
      • check logs of a container – docker logs <container-id>
        • docker logs a15268c9c0be # show full log
        • docker logs –tail 10 a15268c9c0be # show last 10 lines
        • docker logs -f a15268c9c0be # show continuous logs as it generates
      • To stop a container – docker container stop a15268c9c0be
      • To start a container – docker container start a15268c9c0be
      • To kill a container – docker container kill a15268c9c0be
      • Capture
      • to execute redis with a specific port with host container port forwarding( not a good practice because we are hard setting the port)
        • docker run -d –name redisHostStaticPort -p 6379:6379 redis:latest
      • to execute redis with a dynamic host port with host container port forwarding( not a good practice because we are hard setting the port)
        • docker run -d –name redisHostDynamicPort001 -p 6380 redis:latest
        • But now you don’t know which host port was assigned
        • so use command – docker port redisHostDynamicPort001 6380
          • the host port assigned was 32770
        • Now you can run another instance too
          • docker run -d –name redisHostDynamicPort002 -p 6381 redis:latest
          • docker port redisHostDynamicPort002 6381
            • now another port was assigned 32551
        • Now you can see that you are running two instances of redis. See snapshot below.
        • Capture
      • Now to persist the data each time the redis restart we have to define the volumes
        • volumes help you persist the dats from container to the host
        • we can use switch  -v <host-dir>:<container-dir>
        • e.g. docker run -d –name redisHostDynamicPort003 -p 6389 -v “$PWD/data”:/data redis:latest
        • $PWD is to get present working directory
        • $PWD/data means the data folder in current directory of host
        • /data means the /data folder of redis container where logs will be stored
        • -v “$PWD/data”:/data means defining an attaching a volume forwarding from container folder /data to the host folder data
        • Capture
      • check or inspect a container
        • it provides the meta data about the container
        • docker inspect <containerid-or-name>
        • e.g. docker inspect redis
        • docker inspect –format “{{RepoTags}}” redis # searches lines in the inspect JSON
      • Capture
    • Running redis in foreground:
      • docker run -it redis 
      • the switch “-it” runs a container in foreground or interactive mode
      • Capture