DevOps Classroom Series – 29/Mar/2021

Docker Volume mounts

  • Docker Volume Mount types Preview
  • Lets create a docker volume for the apache html folder Preview Preview Preview
  • Start the container with a volume
docker container run -d --name apache1 -P --mount "source=apachehtml,target=/var/www/html" httpd:latest

Preview

  • Now lets verify the mount point in the docker container
docker container inspect apache1

Preview

  • Now lets create some files in the /var/www/html folder from the container Preview
  • Now lets create a new container and mount the same volume into same folder (-v)
docker container run -d --name apache2 -P -v 'apachehtml:/var/www/html' httpd:latest

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  • Now lets delete all the containers
docker container rm -f $(docker container ls -a -q)

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  • Now lets create a new container and use the same volume mount
docker container run -d --name apache3 -P --mount "source=apachehtml,target=/var/www/html" httpd:latest

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  • Volume driver can help in creating volumes in the
    • nfs
    • cifs
    • cloud
  • We need to install volume plugins and then use the volume driver while creating the volume
  • Refer Here for the official docs
  • Sample AWS Volume plugin Refer Here
  • Azure volume driver Refer Here
  • Lets create a Postgres container with volume mounted so that we can preserve the data
  • postgres stores the data in the folder /var/lib/postgresql/data
  • Lets create a postgres container Refer Here Preview
  • Now lets use exec command to create some data in the database Preview Preview
  • Containers can run applications of two types
    • Stateless: These applications donot store any data locally, so we dont need volumes for them
    • Stateful: these applications store the data and this data needs to be preserved so for stateful applications we use docker volumes
  • Useful docker commands
    • docker system df: This command will help in findng out the size of all docker objects in the Host Preview
    • To get more detailed information use docker system df -v Preview
  • To view the logs we can use the docker Preview
  • The other approach of storing logs is create a volume for the /var/logs folder and then export the logs from the docker host to central logs.
  • The other approach is to have a log client inside the container running which exports logs to centralized log server.
  • For tempfs mount Refer Here

Next Steps

  • Multi Staged build
  • docker networking
  • docker compose
  • intro to docker swarm
  • kubernetes
  • helm
  • openshift

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