Docker Basics

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Basics of docker

Dockerfile contains all the commands and base OS details
Image - a unit where all Os, dependencies and config is defined
Container - Instance of an image
docker build -t name:latest. - Builds image from dockerfile
docker images - shows list of images
docker pull image_name - pulls image from dockerhub
docker run -itd -p 8080:80 imagename:latest - start a container from image
- i - interactive
- d - daemon mode
- t - assign false tty
- 8080 - port on host device
- 80 - exposed port in image
docker ps - lists the running containers
docker exec -it ContainerID command
docker run -itd --name newname imagename - create a container named new name from image imagename and execute
docker stop - stops all docker containers
docker rmi - removes all images from disk
docker rm - removes all containers from disk
Note: We can use first 4 characters of container ID instead of the whole ID

docker info - gives info about docker, profiles, storage location
docker inspect imagename - gives info about a particular image
Anyone with root access on host will have complete control over the containers and its contents
Docker forms intermediate layers after each instruction

It helps to limit access to resources availble for containers
Crucial for avoiding forkbombs
find /sys/fs/cgroup/ -name "image name" to find cgroup entries
pid entrys are of great interest
on navigating to folder you can find pids.max - if it is max it is dangerous ❗
docker run -itd --pids-limit 6 imagename - pids-limit sets the pid limit to 6 in this example

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