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A Cloud Guru

Using Volumes in Docker Containers

Containers are designed to be ephemeral, so when you need persistent data, it is usually not a good idea to store it directly in the container's file system. This is where Docker volumes come into play. Docker volumes allow you to store persistent data outside the container itself, providing greater flexibility in what you can do with your data. In this lab, you will have the opportunity to solve a complex problem using Docker volumes. You will have a chance to work with both shared volumes and bind mounts in order to implement two containers which work together, one container transforming data created by the other. This will give you some practice in working with volumes, as well as some insight into the many ways in which Docker volumes can be used.

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Path Info

Level

Intermediate

Duration

45m

Published

Jun 06, 2019

Challenge

Create the shared volume and counter container to generate some sample data.
1. Create a shared volume.
```
docker volume create test-data
```
1. Create the counter container with the provided command, and mount the shared volume to the container.
```
docker run --name counter -d 
  --mount type=volume,source=test-data,destination=/var/log/test 
  busybox 
  sh -c 'i=0; while true; do echo "$i: $(date)" >> /var/log/test/1.log; i=$((i+1)); sleep 1; done'
```
You can confirm that the counter container is generating data by examining the file inside the container:
```
docker exec counter cat /var/log/test/1.log
```

Challenge

Create the fluentd container to transform and output the data from the counter container.

Create the fluentd container and mount the shared volume, the config file, and the output directory to it.

docker run --name fluentd -d 
  --mount type=volume,source=test-data,destination=/var/log/input 
  --mount type=bind,source=/etc/fluentd/fluent.conf,destination=/fluentd/etc/fluent.conf 
  --mount type=bind,source=/etc/fluentd/output,destination=/var/log/output 
  --env FLUENTD_ARGS="-c /fluentd/etc/fluent.conf" 
  k8s.gcr.io/fluentd-gcp:1.30

Verify that the fluentd container is generating output on the Docker host.

ls /etc/fluentd/output

You should see some files containing the transformed log data.

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

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