Hi. Welcome to CodingDroplets. In this video we are
going to see about two important things of docker, docker file and docker compose. We'll be
using both docker file and docker compose while developing the projects in our
upcoming videos. So let's get started. First let's see about docker file. What is a
docker file? Docker can build images automatically by reading the instructions from a docker file. A
dockerfile is a text document that contains all the commands a user could call on the command line to
assemble an image. So we can create a docker file and use docker build command to create an
image from the docker file. Then we can use docker run command to create and run a docker
container from the docker image. Now let's have a look on some of the docker files. You can view
the docker files by clicking on the tags provided in the docker image documentation in docker
hub. Let me open the official image of Redis. In the documentation you can see, there are
several tags available. Let me click on this version with alpine operating system. Here you
can see the docker file for that tag in github. There are several instructions mentioned in the
dockerfile like FROM, RUN, ENV etc. The instructions are not case sensitive, however the convention is
for them to be uppercase to distinguish them from the arguments more easily. Docker treats
lines that begin with hash as a comment. Unless the line is a valid parser directive.
We'll be discussing about parser directives in a later session. Docker runs instructions in a
docker file in order. A docker file must begin with a from instruction. On the top it is mentioned
from alpine 3.15. So alpine:3.15 is a different image. Means this Redis docker image
is using the docker image of alpine and running some commands in it to download and install redis
and run it. Now let's have a look on the alpine's docker image. So let me search for alpine here.
Here you can see the official image of alpine. Let me click on that. So in this docker image
documentation you can see some tags here 3.15, 3.14, 3.13, several versions. So let me click
on the latest version to see the dockerfile. Here you can see the FROM instruction in
the dockerfile and the argument is SCRATCH. So let's find out what is SCRATCH. I'm
searching for scratch docker image and here you can see the docker
image scratch, the official image. I'm clicking on that. So here you can see that
the scratch image is the smallest possible image for docker. It is an empty image. You can
also see the details in the image documentation. So here there is a small example showing
how to use the scratch image. Next let's see some commonly used instructions in
the docker files. First one, FROM. This command allows you to create a base image such as
an operating system, a programming language etc the instructions executed after this
command take place on this base image. Second one, RUN. Used to run specified commands. You can use
several run instructions to run different commands. Third one, CMD. Specifies the instruction that is
to be executed when a docker container starts. Fourth one, ENTRYPOINT. Used to
set executables that will always run when the container is initiated. Unlike CMD
command, Entry Point commands cannot be ignored or overwridden. Fifth one, WORKDIR. To specify
your working directory inside the container. Sixth one, COPY. To copy files or folder from
your local machine to the docker container. Seventh one, ADD. Similar to copy instruction you
can use add instruction to copy files or folders from your local machine to the docker container.
However add instruction also allows you to copy files from a URL or a TAR file. EXPOSE. The
expose instruction inside the docker file informs that the container is listening to the
specified port in the network. The default protocol is TCP. LABEL. To add description or metadata for a
docker image. It's a key value pair. The tenth one is VOLUME. Used to create or mount a volume to the
docker container from the docker host file system. Next is USER. Used to set the user name, group
name, uid or gid for running subsequent commands. If not provided the root user will be used. Next
one ENV. Used to set environment variables with key and value. Next one ARG. Also used to set
environment variables with key and value. But this variable will set only during the image build. Not
on the container. And next one is ONBUILD. Used to specify the commands that runs when the new docker
image is used as a base image for another image. Now let's create a docker image from a dockerfile.
I have already created a docker file which is having three different instructions. It is having
a FROM instruction to use alpine as the base image. Then I have provided a COPY
instruction to copy the folder named sample files. Let's see what we
have in the sample files folder. Here you can see there are three text files and
I need to copy these three files to the container. Finally I have given a command to sleep for two
minutes for just keeping the container running for two minutes. Otherwise the container will
get stopped immediately. So we are not running any other services. If there are no services
running, then the container will get stopped. So I have opened powershell to execute the docker
build command. As I told in the previous video, you can use powershell or command prompt in windows.
If you are using mac or linux, you can use the terminal. So let me provide docker build command.
Then '-t' which is a parameter for assigning a name for the image. So i'm providing 'sample-img'
as the image name. we can also provide the tag along with the image name by separating with a
colon. you can specify a version number if needed. if not provided anything, docker will automatically
assign a latest tag for the image. After that we can provide '-f' parameter which is used to
mention the docker file name. But we don't really need to provide this parameter as we have used the
default docker file name. That is just Dockerfile. So i am just removing the '-f' parameter.
So if you are using a different file name, you can provide '-f'. Then the file name here.
So now currently we are using the default docker file name. We are not providing this parameter.
Then finally, just provide a dot. Then hit enter. Now the alpine latest OS is getting downloaded and finally the image got created. Now I can
see the image using docker images command and you can see here the image name is sample
img. The tag is latest. So as we have not provided a custom tag automatically docker used latest
tag. Then the image id which is a unique id for the image in our machine. Also it is showing
the image size. I can open docker desktop and choose the images option to see the image details.
Here also you can see the image name, tag, image id, then size, all those details. Now let's provide
the docker run command to create container from this image and it will run the container.
So we have to provide the image id as well and now if I open docker desktop, I can see that
the container got created and it is running. So from the docker desktop, we can
open the CLI of this container. So otherwise from the terminal, you can just provide
docker exec -it, then the image id slash bin slash sh. That will open the same terminal or the
same command line for the docker. Now here I'm just providing ls command and you can see here there is
a folder named my files. I'm just providing cd my files to go inside the folder and providing the
ls command. And here you can see we have all the three text files which we had in our sample files
folder. So the files got copied to the container. So next let's move to docker compose. What is
docker compose? Docker Compose is a tool to help define and share multi-container applications. It's
an important tool for any application that needs multiple micro services as it allows each service
to easily be in a separately managed container. How to use docker compose? We can use a YAML file
to configure your application's services. The configuration for a docker compose file is done
in 'docker-compose.yml'. You don't need to place this file at the root of your project
like a docker file. Infact it can go anywhere as it doesn't depend on any other code. However if
you are building the images locally, it will need to go in a project folder with the code being
built. Next we are going to create multi-service containers using docker compose. So in my C folder,
I have created a docker compose file, 'docker-compose.yml'. This is the content of the docker
compose file. In the first line you can see the version of the docker compose. So I am using docker
compose version 3.7. So in the first line of our docker compose file we can mention the version
of the docker compose which we are going to use. Next I have mentioned volume, 'wp-data'.
After that networks, 'wp-network'. After that you can see there are several services.
The first service is db. So I have provided a custom name for the container 'mysql-db'.
and the image which I am going to use is mysql colon 5.7. So 5.7 is the version which
I am going to use. Then I have mentioned volume for the mysql container. After that
I have mentioned the environment variables. It contains mysql root password, mysql
database name, mysql user, mysql password. Then the port number for mysql. So normally it uses
3306. But I have provided a custom port number triple eight nine and finally I have assigned
wp-network for this container. Next service is phpmyadmin I have provided 'php-myadmin' as
the container name and the base image phpmyadmin phpmyadmin and here you can see it is
depending on the db container. After that I have provided the environment variables for
this particular container. Then the port number. I have assigned 8001. After that I have provided
the same network name. Then the final service. That is wordpress. Container name is wordpress-site.
Image is wordpress colon latest. So it will pull the latest version of wordpress and
this container also depends on the db container. Andd provided a custom port number for wordpress,
8002. Then the environment variables for the container and volume and network. Now let's
execute the command for creating the containers for this particular services. So I'm
providing docker-compose space up then '-d' to detach the containers
and that's enough. Now docker compose will pull the images from the repository and create the
containers. So initially it is pulling the mysql image and pulling that image got
completed. Now it is going to pull phpmyadmin and that also completed. Now the
next image is for wordpress, the final image. So all the images got downloaded
successfully and the containers are created. Now the containers are running. So I can use
docker images command to see all the images and you can see we have wordpress, mysql
and phpmyadmin. Now let me provide docker ps command to see the running containers and you
can see all the three containers are running. Now I have opened docker desktop and you can see
here demo wordpress this is the application and if I click on this expand button, it will
show the containers running inside it. So mysql, wordpress and phpmyadmin all are running
fine and here you can also see the port numbers each container is listening to. The first db
container is listening to triple eight nine. Wordpress listening to eight zero zero two.
phpmyadmin listening to eight zero zero one. So let's try to open the URLs. 'localhost:8001' and that is the phpmyadmin and you can
see that phpmyadmin is working fine. Now let me try to open 'localhost:8002' and you can
see now wordpress is also working fine. So here we have got the initial setup page for wordpress.
So that's it for this video. Hope you liked it. Please subscribe, like and share this video.
See you all in the next video. Thank You!
