in this section we will start off with mounting volumes between containers
the key command here is volumes-from and the syntax is as below
docker run --name website-copy --volumes-from website -d -p 8081:80 nginx
dockerfile allows us to create our own images .
docker image ls
the above command will list all of the images we have
in ide , create a file and name it Dockerfile , start with the FROM keyword and mention the base image. In this case , its going to be nginx , so thats the base image and the second line is really adding the current directory of the host to the path specified where it will be mounted inside the container , so the dockerfile should look like this
FROM nginx:latest
ADD . /usr/share/nginx/html
save the dockerfile. go the directory where the code is and type in the command below
docker build --tag website:latest . Sending build context to Docker daemon 4.071MB
Step 1/2 : FROM nginx:latest
---> 992e3b7be046
Step 2/2 : ADD . /usr/share/nginx/html
---> ec6fa782dfbf
Successfully built ec6fa782dfbf
Successfully tagged website:latest
SECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.
the “.” after the tag indicates current directory and thats where the docker file is kept , so it copes the base image from step 1 and then add the current files to the container dest directory in step 2 . notice the default set of permissions.
type in docker image ls to check if the new images are available
docker image ls REPOSITORY TAG IMAGE ID CREATED SIZE
website latest ec6fa782dfbf 3 minutes ago 137MB
nginx latest 992e3b7be046 7 days ago 133MB
now lets run a container off the newly created image
PS C:\training\dockertrng> docker run --name website -p 8080:80 -d website:latest 835d06b0801c3233c5009724c893feedcb18e745dcc8ffee901c21f21d48f4c1
PS C:\training\dockertrng> docker ps --format=$FORMAT ID 835d06b0801c
Name website
Image website:latest
Ports 0.0.0.0:8080->80/tcp
Command "/docker-entrypoint.…"
Created 2020-10-12 18:39:56 -0400 EDT
Status Up 10 seconds
as you can see the container is named website and its running off the the image website:latest .
lets create a container that runs node and express . Install node and then follow the hello world instruction given for express and now the goal is to run the same as a docker container. So just like before we need to create a dockerfile and it will look like this .
FROM node:latest
WORKDIR /app
ADD . .
RUN npm install
CMD node index.js
the ADD . . is confusing , but here is the interpretatiion , the first . represents the current directory where the docker build command would run and the second . represents the workdir in other words /app directory that was specified in the line above . so this is what you get when you run the docker build command.
docker build -t user-service-api:latest .
Sending build context to Docker daemon 2.01MB
Step 1/5 : FROM node:latest
---> f47907840247
Step 2/5 : WORKDIR /app
---> Using cache
---> 0c9323ed7812
Step 3/5 : ADD . .
---> e0b87ce6045f
Step 4/5 : RUN npm install
---> Running in 8ffa6f7451e8
npm WARN user-service-api@1.0.0 No description
npm WARN user-service-api@1.0.0 No repository field.
audited 50 packages in 0.654s
found 0 vulnerabilities
Removing intermediate container 8ffa6f7451e8
---> a9780fbcaf7e
Step 5/5 : CMD node index.js
---> Running in a6633c49b9ef
Removing intermediate container a6633c49b9ef
---> d6c4df7196aa
Successfully built d6c4df7196aa
Successfully tagged user-service-api:latest
SECURITY WARNING: You are building a Docker image from Windows against a non-Windows Docker host. All files and directories added to build context will have '-rwxr-xr-x' permissions. It is recommended to double check and reset permissions for sensitive files and directories.
At this point an image has been created based on the dockerfile and it has the node and the index.js file that we need. so if we spin up a container based on that image , then we get the desired output
docker run --name websitesv -d -p 3000:3000 user-service-api:latest
2d475dccd375995e5af09b96e4bc85045235d20fe88a7fccccba80d9bc793719
Now if you go to localhost:3000 , it should give you the response based on the code in index.js
lets look at .dockerignore file
this file is used to ignore any files or folder in the current directory that does not need to be added to the container workdirectory . in the example above we are copying the dockerfile , the node modules and possibly the .git file in the docker container even though we dont need it. the .dockerignore file gives us the abilty to ignore these files when the image is created . Basically create a .dockerignore file in he same dir as dockerfile and add the following to the same and then run the build statement
node_modules
Dockerfile
.git
the build will download the node packages everytime and this makes the process slow . The more efficient approach is to enable the use of caching and this can be done by stating the package*.json file and npm install explicitly and this ensures that cache is used sunce docker may not detect changes in those directories
FROM node:latest
WORKDIR /app
ADD package*.json ./
RUN npm install
ADD . .
CMD node index.js