A container’s temporary filesystem is isolated from any other container or Pod and is not persisted beyond a Pod restart. A Pod can define a Volume and mount it to a
container.
Ephemeral Volumes exist for the lifespan of a Pod. They are useful if you want to share data between multiple containers running in the Pod. Persistent Volumes preserve data beyond the lifespan of a Pod. They are a good option for applications that require data to exist longer, e.g., in the form of storage for a database-driven application. In this chapter, we’ll exercise the use of different Volumes types in a Pod.
Working with Storage
Applications running in a container can use the temporary filesystem to read and write files. In case of a container crash or a cluster/node restart, the kubelet will restart the container. Any data that had been written to the temporary filesystem is lost and cannot be retrieved. The container effectively starts with a clean slate.
There are many uses cases for wanting to mount a Volume in a container. We’ll see one of the most prominent use cases in Chapter 8: using an ephemeral Volume to exchange data between a main application container and a sidecar. Figure 7-1 illustrates the differences between the temporary filesystem of a container and the use of a Volume.
Figure 7-1. A container using the temporary filesystem ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month, and much more.
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.
Julian F.
Head of Cybersecurity
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.
Addison B.
Field Engineer
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.
Amir M.
Data Platform Tech Lead
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.
