DevOps Classroom Series – 29/Mar/2021

Docker Volume mounts

• Docker Volume Mount types
• Lets create a docker volume for the apache html folder
• Start the container with a volume

docker container run -d --name apache1 -P --mount "source=apachehtml,target=/var/www/html" httpd:latest

• Now lets verify the mount point in the docker container

docker container inspect apache1

• Now lets create some files in the /var/www/html folder from the container
• 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

• Now lets delete all the containers

docker container rm -f $(docker container ls -a -q)

• 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

• 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
• Now lets use exec command to create some data in the database
• 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
  • To get more detailed information use docker system df -v
• To view the logs we can use the docker
• 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