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Building_own_images.md

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Understanding a dockerfile

# defines base image
FROM microsoft/dotnet:1.1-sdk
# set the working directory for following commands
WORKDIR /app

# copy csproj and restore as distinct layers
COPY net_core_console.csproj ./
# restore nuget packages
RUN dotnet restore

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

# define the entry point when the container gets executed
ENTRYPOINT ["dotnet", "out/net_core_console.dll"]

Recommendations by the docker community

Create your own image

What could be useful

but wait there are more ... Dockerfile reference

and here are some more commands regarding images ... Image commands

Tip:

  • structure an image around change use layering e.g. only restore nuget packages if you changed something
  • use trusted registry / official images as base images

Security concerns:

  • use vulnerability scans (docker offers out of the box checks)
  • check out docker notary (image signing + trusted registry)

Build the image


# using a Dockerfile in the current directory
docker build -t myimage:0.1 .

# or specifiy the dockerfile using -f
docker build -t myimage:0.1 -f ./MySuperDockerfile

Run your image

docker run --rm -it myimage:0.1

Working with your local registry

# check your local registry
docker image ls

# remove an image
docker rmi {image id}
docker image rm {image id}

# see what happend
docker image history

# and the other commands
# ----------------------------------
docker image --help

Usage:  docker image COMMAND

Manage images

Options:
      --help   Print usage

Commands:
  build       Build an image from a Dockerfile
  history     Show the history of an image
  import      Import the contents from a tarball to create a filesystem image
  inspect     Display detailed information on one or more images
  load        Load an image from a tar archive or STDIN
  ls          List images
  prune       Remove unused images
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rm          Remove one or more images
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

Run 'docker image COMMAND --help' for more information on a command.

Make some code changes

  1. Edit your Progam.cs
  2. Build again
  3. run it
# here is how it could look like :)

D:\Git\docker_for_dot_net_devs\src\net_core_console (master)
λ docker build -t sibica/console:0.1 .
Sending build context to Docker daemon 7.168 kB
Step 1/7 : FROM microsoft/dotnet:1.1-sdk
 ---> 5ff94bceebcf
Step 2/7 : WORKDIR /app
 ---> Using cache
 ---> 4971e1153302
Step 3/7 : COPY net_core_console.csproj ./
 ---> Using cache
 ---> 51
Step 4/7 : RUN dotnet restore
 ---> Using cache
 ---> 9b1734a1dd94
Step 5/7 : COPY . ./
 ---> 3d547c2cf65e
Removing intermediate container 670da65e1f40
Step 6/7 : RUN dotnet publish -c Release -o out
 ---> Running in c07e72b0664a
Microsoft (R) Build Engine version 15.1.1012.6693
Copyright (C) Microsoft Corporation. All rights reserved.

  net_core_console -> /app/bin/Release/netcoreapp1.1/net_core_console.dll
 ---> 13b538987226
Removing intermediate container c07e72b0664a
Step 7/7 : ENTRYPOINT dotnet out/net_core_console.dll
 ---> Running in 496ffc57d054
 ---> 42
Removing intermediate container 496ffc57d054
Successfully built 42
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.

D:\Git\docker_for_dot_net_devs\src\net_core_console (master)
λ docker run --rm -it sibica/console:0.1
Hello World! From Docker

Tagging

why it's useful? tagging documentation (How to tag an image )

Some examples for tagging

When working with windows use other escape character !

Multi stage containers

** If your running docker for windows => you need the edge channel !**

http://training.play-with-docker.com/multi-stage/

Here is an example for the console app

#Builder
FROM microsoft/dotnet:1.1-sdk

# copy all source
COPY . /myapp
RUN dotnet restore ./myapp && \
    dotnet build -c release ./myapp && \
    dotnet publish -c release -o pubdir ./myapp

#Final Build
FROM microsoft/dotnet:1.1-runtime
COPY --from=0 /myapp/pubdir /myapp

ENTRYPOINT ["dotnet", "/app/net_core_console.dll"]