https://devopsschool.com/tutorial/docker/dockerfile/dockerfile-example-sample-lab.html Docker File 1: /usr/sbin/apache2ctl specified in CMD will run in foreground as a blocking call. Docker File 2: Just exit after echoing “Hello world”. Docker File 3: Just exit after echoing “Hello”. Docker File 4: Same as ‘Docker File 1‘ except port 80 will be shown as exposed port. Docker File 5: Output will be print like : “Hello /bin/sh -c echo “Hello world””. First it will execute ENTRYPOINT then content of CMD will be passed as an arument

Dockerfile with 2 CMD, 2 ENTRYPOINT: File content: Output: Welcome to /bin/sh -c echo “DOCKER” Observations: Both CMD and ENTRYPOINT entries will be overwritten with the latest entries. That is only the last CMD and ENTRYPOINT will be taken. Also the values specified in CMD will be add as an argument to the ENTRYPOINT command. Dockerfile with 1 CMD, 1 ENTRYPOINT: File content: Output: Hello World Observations: Values specified in CMD will be add as an argument to the ENTRYPOINT

both cmd and entry point cannot come together for a web application

1) FROM : must be the first non-comment instruction in the Dockerfileeg : FROM ubuntu2) MAINTAINER :instruction allows you to set the Author field of the generated imageseg : MAINTAINER Mani K.M mani.km@quest-global.command3) RUN : The exec form makes it possible, to RUN commands using a base image that does not contain the specified shell executableeg: RUN apt-get update4) CMD: The main purpose of a CMD is to provide defaults for an executing containereg : CMD echo Hello world5) LABEL

FROM – Sets the base imageMAINTAINER – Sets the author field of the generated imagesRUN – Execute commands in a new layer on top of the current image and commit the resultsCMD – Allowed only once (if many then last one takes effect)LABEL – Adds metadata to an imageEXPOSE – Informs container runtime portENV – Sets an environment variableADD – Copy new files, directoriesCOPY – Copy new files or directories into the filesystem of the containerENTRYPOINT – Allows you to

Q1. List out all INSTRUCTION statement of dockerfile and give one line explanation.Environment variables are supported by the following list of instructions in the Dockerfile: ADD -> check if compressed file and copying the content to docker containerCOPY -> Just copying the content to docker containerEXTRACT -> Extract the content to specified location in docker container ENV -> for setting the environment valuesEXPOSE -> exporting the port of the application to outside container. FROM -> pull the docker imageLABEL ->

FROM – creates a layer from the base imageeg : FROM ubuntu:18.04 MAINTAINER – The MAINTAINER instruction allows you to set the Author field of the generated images.RUN – builds your application with makeeg : RUN make /appCMD – specifies what command to run within the containerLABEL – The LABEL instruction adds metadata to an image.EXPOSE – Informs Docker that the container listens on the specified network port(s) at runtime.ENV – The ENV instruction sets the environment variable to the

FROM: The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructionsRUN: The RUN instruction will execute any commands in a new layer on top of the current image and commit the results.MAINTAINER: The MAINTAINER instruction sets the Author field of the generated images.EXPOSE: The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtimeENV: The ENV instruction sets the environment variable to the valueADD: The ADD instruction copies new

Sceraniro 1 2 CMD – the last CMD will override the first one Scenario 2 2 EntryPoint – the last ENTRYPOINT will override the first one Scenario 3 1 ENTRYPOINT and 1CMD – Entrypoint will override CMD

FROM – Mention a docker image name. Ex: FROM ubuntu MAINTAINER – Mention about the author who create the docker file. Ex: MAINTAINER BittoKC RUN – To execute any command on the container. Ex: RUN touch /tmp/file1.txt ARG – To set an environment variable. Ex: ARG USER1 gehc_security EXPOSE – To specify about the network port that container use at runtime. Ex: EXPOSE 80 COPY – To copy files/directories within the file system of docker. Ex: COPY /tmp/file1.txt . ADD

FROM – to specify the parent image. Eg ubuntu from which you create an imageMAINTAINER – to set the author/creater of the imageRUN – to run a command like shell script in linux or execute a programARG – should be used along with FROM to speficy any arguments lie versionEXPOSE – To inform the docker that the container listern on the given portCOPY – to copy files or dir to the container destination pathADD – to copy files or dir

Test1: docker run 27d064e1c81aHEllo from second entrypoint /bin/sh -c echo “Hello world from second cmd” Test2: root@ip-172-31-28-155:/home/ubuntu/raju# docker run 27d064e1c81a echo testHEllo from second entrypoint echo test Explanation: Only the second cmd or entrypoint is being considered. Moreover if we try to replace cmd during run time then second entrypoint and run time cmd is considered.

FROM – First command inside a docker file and Creates the base image. MAINTANER – Sets the author info of docker file. RUN – Runs command in the container of previous layer ARG -Sets the variable EXPORT -Expose a port COPY – Copies a file to the container ADD – copies a files from source location to a image location WORKDIR -Sets working directory CMD – To run a command or executable ENTRYPOINT Sets PID1 VOLUME-Creates a mount point USER

FROM -It should be the first instruction in the Dockerfile. It is used to specify our base layer from which we are creating the image. MAINTAINER – It is used to set the author. RUN – It is used to run a command in shell. CMD – It provides a default executable for a container. LABEL – It is used for putting some metadata in a container. EXPOSE – Expose a port and listens to it. ENV – Used to

FROM – base image to start creating the new image RUN – Run command in a container created from previous line/layer ARG – Set a variable for docker file execution and reuse using $(varname) ENV – Meta layer to set environment for the container EXPOSE – Sepcify information port for the container and also can be used during port forwarding COPY – Copy the file in same location as Docker file to container locationADD – Copy the file in same

Storage driver is a software that allows you to write data to the writable layer of your Docker container. Types of storage driver • overlay2 – This is the preferred storage driver for all Linux distributions• aufs – Preferred driver for earlier versions of Docker, when running on an earlier version of Ubuntu.• devicemapper – Was the recommended driver for earlier versions of Centos and RHEL. Current versions support overlay2, which is the recommended driver.• btrfs – Used if this

Created an image docker run –name sree -itd centosb50dcbcba771a111bf7c0b9a08eb4f14acfb83c666b2d5f8afbc13a7afc0748eroot@ip-172-31-28-155:/home/ubuntu# docker ps|grep sreeb50dcbcba771 centos “/bin/bash” 15 seconds ago Up 14 se conds sreeroot@ip-172-31-28-155:/home/ubuntu# docker attach sreeyum install git -yyum install httpddocker commit -a”sreerekha” -m”ce-git-httpd -sree” sree ce-git-httpd-sree docker imagesREPOSITORY TAG IMAGE ID CREATED SIZEce-git-httpd-sree latest b50885a6b058 19 seconds ago 346MB docker run –name rekha -itd ce-git-httpd-sree0d9262edc8ec86f142dc3fcb0b78cd1b923f9003ca022aa4a68b258bf6b0efc9root@ip-172-31-28-155:/home/ubuntu# docker ps|grep rekha0d9262edc8ec ce-git-httpd-sree “/bin/bash” 17 seconds ago Up 16 seconds rekha docker exec rekha git –versiongit version 2.27.0

root@ip-172-31-28-155:/var/lib/docker/overlay2# docker run -itd –name anoop_centos_2 centos460aebb7de8bde42112d32e5e37df7617fb8e0588a9bdccf79f47d98357cede7 [root@ip-172-31-28-155:/var/lib/docker/overlay2# docker ps | grep anoop460aebb7de8b centos “/bin/bash” 4 seconds ago Up 3 seconds anoop_centos_2 root@ip-172-31-28-155:/var/lib/docker/overlay2# docker attach 460aebb7de8b [root@460aebb7de8b /]# yum update [root@460aebb7de8b /]# yum install git [root@460aebb7de8b /]# yum install epel-release [root@460aebb7de8b /]# yum install -y ntp –> failed [root@460aebb7de8b /]# yum install httpd [root@460aebb7de8b /]# read escape sequenceroot@ip-172-31-28-155:/var/lib/docker/overlay2# docker ps | grep anoop460aebb7de8b centos “/bin/bash” 12 minutes ago Up 12 minutes anoop_centos_2 root@ip-172-31-28-155:/var/lib/docker/overlay2# docker commit -a “anoop” -m “centos with

1.Docker Image is like a template from which we can create docker containers 2.Docker images have multiple layers 3.Writable layer is only the upper layer which will be created when we are creating a container 4.Docker images get stored in public or private repositories 5.Docker images can be created either by manually or using docker file 6.The read-only layers of an image can be shared between any container started from the same image. 7.Size is the size used by writable