STEP5. Update the package database with the Docker packages from the newly added repo:
sudo apt update
STEP6. Make sure you are about to install from the Docker repo instead of the default Ubuntu repo:
apt-cache policy docker-ce
STEP7. Finally, install Docker:
sudo apt install docker-ce
STEP8.Docker should now be installed, the daemon started, and the process enabled to start on boot. Check that it’s running:
sudo systemctl status docker
STEP9. Avoid typing sudo whenever you run the docker command, add your username to the docker group:
sudo usermod -aG docker ${USER}
STEP10. To apply the new group membership, log out of the server and back in, or type the following:
su - ${USER}
STEP11. Confirm that your user is now added to the docker group by typing:
id
STEP12.If you need to add a user to the docker group that you’re not logged in as, declare that username explicitly using:
sudo usermod -aG docker ${USER}
STEP13. Start Docker Server.
sudo service docker start
STEP14. Docker run helloworld error and resolved method
~$ docker run helloworld
Unable to find image 'helloworld:latest' locally
docker: Error response from daemon: pull access denied for helloworld, repository does not exist or may require 'docker login': denied: requested access to the resource is denied.
See 'docker run --help'.
~$ docker login
Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.
Username: lqwangxg
Password:
WARNING! Your password will be stored unencrypted in /home/wangxg/.docker/config.json.
Configure a credential helper to remove this warning. See
Build cache is only used from images that have a local parent chain. This means that these images were created by previous builds or the whole chain of images was loaded with docker load. If you wish to use build cache of a specific image you can specify it with --cache-from option. Images specified with --cache-from do not need to have a parent chain and may be pulled from other registries.
BuildKit
Starting with version 18.09, Docker supports a new backend for executing your builds that is provided by the moby/buildkit project. The BuildKit backend provides many benefits compared to the old implementation. For example, BuildKit can:
Detect and skip executing unused build stages
Parallelize building independent build stages
Incrementally transfer only the changed files in your build context between builds
Detect and skip transferring unused files in your build context
Use external Dockerfile implementations with many new features
Avoid side-effects with rest of the API (intermediate images and containers)
Prioritize your build cache for automatic pruning
To use the BuildKit backend, you need to set an environment variable DOCKER_BUILDKIT=1 on the CLI before invoking docker build.
4. Docker Languages Type:
# Comment
INSTRUCTION arguments
5. Go into the container of docker.
docker exec -it <ContainerID> /bin/bash
*on alpine, no bash but sh. /bin/sh will be ok
6. docker -v
docker run -it -v c:\Data:c:\shareddata microsoft/windowsservercore powershell
docker run -dp 3000:3000 ` #in bash shell use \ for continue next row -w /app -v "$(pwd):/app"` #in power shell use` for continue next row node:12-alpine ` sh -c "yarn install && yarn run dev" #use yarn(like npm) to install and run.
14.Show logs of Container
docker logs -f <container_id>
$ nodemon src/index.js
[nodemon]1.19.2
[nodemon] to restart at any time, enter `rs`[nodemon] watching dir(s): *.*
[nodemon] starting `node src/index.js`
Using sqlite database at /etc/todos/todo.db
Listening on port 3000
15.Multi-Container Apps
Caustion: each container should do one thing and do it well.
16. Create the network
docker network create todo-app
17.Start a MySQL container and attach it the network.
docker run -d \ #in bash shell, \ for continue next row. --network todo-app --network-alias mysql \ -v todo-mysql-data:/var/lib/mysql \ -e MYSQL_ROOT_PASSWORD=secret \ -e MYSQL_DATABASE=todos \ mysql:5.7
18. To Confirm the mysql database up and running.
docker exec -it <mysql-container-id> mysql -p when the password prompt comes up, type in secret. then mysql> SHOW DATABASES;
You should see output that looks like this:
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| todos |
+--------------------+
5 rows in set (0.00 sec)
19. Use nicolaka/netshoot container(which ships a lot of tools), for troubleshooting or debugging networking issues.
docker run -it --network todo-app nicolaka/netshoot
Inside the container, we're going to use the dig command(DNS tool) dig mysql
And you'll get an output like this...
; <<>> DiG 9.14.1 <<>> mysql
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32162
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;mysql. IN A
;; ANSWER SECTION:
mysql. 600 IN A 172.23.0.2
;; Query time: 0 msec
;; SERVER: 127.0.0.11#53(127.0.0.11)
;; WHEN: Tue Oct 01 23:47:24 UTC 2019
;; MSG SIZE rcvd: 44
20. Run the App with MySQL on dev-mode
First there will be some enviroment variables set.
The docker-compose.yml contents: ---------------------------------------------
version:"3.7"
services:app:image:node:12-alpinecommand:sh -c "yarn install && yarn run dev"ports:-3000:3000working_dir:/appvolumes:-./:/appenvironment:MYSQL_HOST:mysqlMYSQL_USER:rootMYSQL_PASSWORD:secretMYSQL_DB:todosmysql:image:mysql:5.7volumes:-todo-mysql-data:/var/lib/mysqlenvironment:MYSQL_ROOT_PASSWORD:secretMYSQL_DATABASE:todosvolumes:todo-mysql-data:
22. Running Application Stack By docker-compose.yml file
docker-compose up -d -d: run everything in the background
23. Image Building Best Practices
1.Use the docker image history command to see the layers in the getting-started image you created earlier in the tutorial.
You should get output that looks something like this (dates/IDs may be different).
IMAGE CREATED CREATED BY SIZE COMMENT
a78a40cbf866 18 seconds ago /bin/sh -c #(nop) CMD ["node" "src/index.j… 0B
f1d1808565d6 19 seconds ago /bin/sh -c yarn install --production 85.4MB
a2c054d14948 36 seconds ago /bin/sh -c #(nop) COPY dir:5dc710ad87c789593… 198kB
9577ae713121 37 seconds ago /bin/sh -c #(nop) WORKDIR /app 0B
b95baba1cfdb 13 days ago /bin/sh -c #(nop) CMD ["node"] 0B
<missing> 13 days ago /bin/sh -c #(nop) ENTRYPOINT ["docker-entry… 0B
<missing> 13 days ago /bin/sh -c #(nop) COPY file:238737301d473041… 116B
<missing> 13 days ago /bin/sh -c apk add --no-cache --virtual .bui… 5.35MB
<missing> 13 days ago /bin/sh -c #(nop) ENV YARN_VERSION=1.21.1 0B
<missing> 13 days ago /bin/sh -c addgroup -g 1000 node && addu… 74.3MB
<missing> 13 days ago /bin/sh -c #(nop) ENV NODE_VERSION=12.14.1 0B
<missing> 13 days ago /bin/sh -c #(nop) CMD ["/bin/sh"] 0B
<missing> 13 days ago /bin/sh -c #(nop) ADD file:e69d441d729412d24… 5.59MB Each of the lines represents a layer in the image. The display here shows the base at the bottom with the newest layer at the top. Using this, you can also quickly see the size of each layer, helping diagnose large images.
Layer Caching¶
An important lesson to learn to help decrease build times for your container images is using Layer Caching.
Once a layer changes, all downstream layers have to be recreated as well
So, Restructure our Dockerfile to help support the caching of the dependencies.For Node-based applications,we only recreate the yarn dependencies if there was a change to the package.json.
Update the Dockerfile to copy in the package.json first, install dependencies, and then copy everything else in.
Create a file named .dockerignore in the same folder as the Dockerfile with the following contents.
node_modules
.dockerignore files are an easy way to selectively copy only image relevant files
Build a new image using docker build
docker build -t getting-started .
Multi-Stage Builds¶
Separate build-time dependencies from runtime dependencies
Reduce overall image size by shipping only what your app needs to run
Each instruction creates one layer:
FROM creates a layer from the ubuntu:18.04 Docker image.
COPY adds files from your Docker client’s current directory.
RUN builds your application with make.
CMD specifies what command to run within the container.
Minimize the number of layers
Only the instructions RUN, COPY, ADD create layers. Other instructions create temporary intermediate images and do not increase the size of the build.
Where possible, use multi-stage builds, and only copy the artifacts you need into the final image. This allows you to include tools and debug information in your intermediate build stages without increasing the size of the final image.
Pipe Dockerfile through stdin
docker build -t myimage:latest -<<EOF
FROM busybox
RUN echo "hello world"
EOF
BUILD FROM A LOCAL BUILD CONTEXT, USING A DOCKERFILE FROM STDIN
Avoid and or copy, using curl from URL. Avoid doing things like:
ADD http://example.com/big.tar.xz /usr/src/things/RUN tar-xJf /usr/src/things/big.tar.xz -C /usr/src/things
RUN make -C /usr/src/things all
And instead, do something like:
RUN mkdir -p /usr/src/things \
&& curl -SL http://example.com/big.tar.xz \
| tar-xJC /usr/src/things \
&& make -C /usr/src/things all
Maven/Tomcat Example
When building Java-based applications, a JDK is needed to compile the source code to Java bytecode. However, that JDK isn't needed in production. Also, you might be using tooks like Maven or Gradle to help build the app.Those also aren't needed in our final image, Multi-stage builds help.
FROM maven AS build
WORKDIR /app
COPY . .
RUN mvn package
#The above will not be import to the image. Just using them to compile java.
When building React applications, we need a Node enviroment to compile the JS code(typically JSX), SASS stylesheets, and more into static HTML, JS and CSS. If we are't doing server-side rendering, we don't even need a Node enviroment for our production build. Why not ship the static resources in a static nginx container?
FROMnode:12ASbuildWORKDIR /appCOPY package* yarn.lock ./
RUN yarn install
COPY public ./public
COPY src ./src
RUN yarn run build
#The above is just for compiling to html, js, css.
