After we learned a little bit a docker and containers, let's use docker for what it was meant to :) I have created a simple HTTP server which listens on port: 1234

Source code you can see in my Git

Packaging application in image, we call dockerize and it is done pretty simle.

Firstly, you need a Dockerfile in the place of your project. Since my project is on C#.NET Core, I have used the following Dockerfile

FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build-env
WORKDIR /app

# Copy csproj and restore as distinct layers
COPY *.csproj ./
RUN dotnet restore

# Copy everything else and build
COPY . ./
RUN dotnet publish -c Release -o out

# Build runtime image
FROM mcr.microsoft.com/dotnet/core/aspnet:2.2
WORKDIR /app
COPY --from=build-env /app/out .
ENTRYPOINT ["dotnet", "HttpServerDemo.dll"]

Now, let's go through the steps:

• Workdir - The workdir on the container which will be used.
• FROM - The external resources which will be used.
• COPY & RUN - These are self explanatory I hope.

You have to verify you have docker at least 17.05 or newer. My current one is 19.03:

[root@postgresqlpgpool netcoreapp3.1]# docker --version
Docker version 19.03.5, build 633a0ea

The building is also done fairy simple.

[root@postgresqlpgpool HttpServerDemo]# docker build -t httpserverdemo .
Sending build context to Docker daemon  398.3kB
Step 1/10 : FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build-env
 ---> 2fe8fe202baf
Step 2/10 : WORKDIR /app
 ---> Using cache
 ---> 931056fe84ac
Step 3/10 : COPY *.csproj ./
 ---> Using cache
 ---> 33c701ccd6cf
Step 4/10 : RUN dotnet restore
 ---> Using cache
 ---> 2acbc600037a
Step 5/10 : COPY . ./
 ---> 68177b9bdcf6
Step 6/10 : RUN dotnet publish -c Release -o out
 ---> Running in 34db589b7d0b
Microsoft (R) Build Engine version 16.4.0+e901037fe for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  Restore completed in 127.94 ms for /app/HttpServerDemo.csproj.
  HttpServerDemo -> /app/bin/Release/netcoreapp3.1/HttpServerDemo.dll
  HttpServerDemo -> /app/out/
Removing intermediate container 34db589b7d0b
 ---> d81f005279bc
Step 7/10 : FROM mcr.microsoft.com/dotnet/core/aspnet:3.1
 ---> 5b704ff3cb6b
Step 8/10 : WORKDIR /app
 ---> Using cache
 ---> e35d6ba6b507
Step 9/10 : COPY --from=build-env /app/out .
 ---> dc3b27c05e4d
Step 10/10 : ENTRYPOINT ["dotnet", "HttpServerDemo.dll"]
 ---> Running in ff14d57a08fc
Removing intermediate container ff14d57a08fc
 ---> 46b4167e5b2d
Successfully built 46b4167e5b2d
Successfully tagged httpserverdemo:latest
[root@postgresqlpgpool HttpServerDemo]#

You can list the images as follows:

[root@postgresqlpgpool netcoreapp3.1]# docker images
REPOSITORY                             TAG                 IMAGE ID            CREATED             SIZE
httpserverdemo                         latest              4ab730ac8ab5        6 hours ago         207MB

Once the image has been built, you can start the container using that image:

[root@postgresqlpgpool HttpServerDemo]# docker run -d httpserverdemo 80:1234
c23e4bb41a9f660f8b409addb58d398b98dce38e93da00682214141f5bc719c9
[root@postgresqlpgpool HttpServerDemo]#

Finally, you can check the container:

[root@postgresqlpgpool netcoreapp3.1]# docker container ls
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                  NAMES
9afb2dcbd6c2        httpserverdemo      "dotnet HttpServerDe…"   5 hours ago         Up 5 hours          0.0.0.0:80->1234/tcp   web
[root@postgresqlpgpool netcoreapp3.1]#