Docker image is a collection of files systems A docker image acts as a blueprint for docker container. File systems are layered over each other Layer 0 must contain a root filesystem Each layer in image will have 40 character length UUID generated by SHA 256 algorithm. The topmost layer will have priority. All layers in a docker image is Read only. All layers in an image is combined to form a container. From one image multiple containers can be

Images are the base of a container. Images are like classes and containers are like objects. We can create any number of containers from an image. Images can be created from Dockerfile or we can pull from registry. Images can have multiple layers. Images have root file systems , PID, USER namespace etc. Image layers are named with SHA256 algorithm.

Docker supports several storage drivers, using a pluggable architecture. The storage driver controls how images and containers are stored and managed on your Docker host. Docker uses storage drivers to store image layers Docker uses storage drivers to store data in the writable layer of a container. The container’s writable layer does not persist after the container is deleted, but is suitable for storing temp data generated at runtime. Storage drivers are optimized for space efficiency. But write speeds are

Storage drivers are used to write to the container’s writable layer. overlay2 is the most commonly used storage driver nowadays. overlay2 is the default storage driver.

Storage drivers are used to store data in containers writeable layer. The data in storage driver doesnt persist when container is deleted Types of storage drivers are: overlay overlay2 aufs devicemapper fuse-overlayfs vfs btrfs

Q1. – What is the use of “docker update” commands? with example and image “docker update” is used to limit the usage of resources a container can use. CPU usage can be limited by CPU time, no.of CPUs used, or which CPUs are used. Memory usage can be limited for Main Memory as well as Swap Disk IO can be limited by specifying a relative weight. No.of PIDs container can allocate can be limited. This command can also be used

This command is used for waiting one or more containers to stop. We have to open 2 terminals. In one of them just put docker wait and in the other try to stop the same container. We can see the first terminal with docker wait is returned 0 and stopped waiting. docker wait renamed1 [Terminal1] docker stop renamed1 [Terminal2]

It is used for updating container’s configuration. A container have different configurations. We can change those configurations via docker update command. docker update –restart=on-failure:3 renamed1 In the above example we are changing the restart policy of a container.

The docker update command dynamically updates container resources. we can use theses command to configure the containers CPU usage, memory and restart setups $ docker update –cpu-shares 512 abebf7571666

The docker update command dynamically updates container configuration like cpu, memory etc. To specify more than one container, provide space-separated list of container names or IDs.

1. rabbitmq – https://hub.docker.com/_/rabbitmq 2. nginx – https://hub.docker.com/_/nginx 3. fluentd – https://hub.docker.com/_/fluentd 4. prometheus – https://hub.docker.com/r/ubuntu/prometheus 5. kibana – https://hub.docker.com/_/kibana

docker wait will wait for the containers to stop and then print the exit code from the container

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The docker update command dynamically updates container configuration. 

The wait command will wait until a container stops and then print their exit codes.eg docker run –name kphttpd httpd docker wait kphttpd docker kill kphttpd