Debug School: Mayank

How can we store container data in memory using docker volume

Mayank — Wed, 16 Nov 2022 05:36:04 +0000

We can use docker tmpfs volume to store container data in host's memory on linux.
This is used when we don't want to write sensitive data or data that relates to non-persistent application state in the container layer or on the host FS.

What is a Docker image. Explain in 10 points.

Mayank — Tue, 15 Nov 2022 06:48:21 +0000

docker images are stored in hub.docker.com called registry.
All the layers have relationship with each other if you are pulling the top layer the parent layer will be pulled automatically
It's the layers of file system
Docker image consists of multiple filesystems -- ROOTFS + USERFS + ...
Docker image has file system versioning.
For encrypting docker images, sha2-256bit algorithm is used.
All these layers merge to create one layer called mount.
We can see the layer information using "df -kh" and also the memory using "du -h --max-dept=1"
When we start a container there is a merge layer will get created, which is the combination of all the layers which we have pulled
When we add some data into the container and even we stopped the container after that, the data will be available under overlay2 folder as a layer, and it will get attached to the container once is started.

Diff btw docker update and docker wait.

Mayank — Tue, 15 Nov 2022 05:13:55 +0000

What is the use of docker update command?
docker update is used to update configs of one or more containers. We can set cpu resources,restart policy, memory limitations etc of containers using this command.

What is the use of Docker wait?
Docker wait container blocks until the container is exited and returns the exit code.

My basic understanding regarding docker and containers.

Mayank — Mon, 14 Nov 2022 07:19:51 +0000

What is Docker?
Docker is a container management system. Each container run in an isolated manner. each container is responsible for its assigned application to run so docker enables user to build, deploy, run containers so using single OS image.
Why docker?
Cost effective, easy to manage, no worries to purchase different OS license.
What is container?
Container is like an instance of an OS on which only limited things are installed which are necessary to run an application for which container is instantiated. They provide the similar functionality like of a VM but with virtualize OS.
Docker workflow?
USer>>docker client>>docker host>>docker registry>>docker image
How container created?
docker helps in creating container with the help of kernel on which docker is installed.