"Docker build path not found" in docker support Visual Studio Project

Question

I have C# solution, with 4 projects, 3 being Dlls and 1 is the console application uses those DLLs.

I tried to use docker support on visual studio to build my docker image, it fails My dockerfile as below:

> FROM microsoft/windowsservercore:ltsc2016 
> EXPOSE 80 
> EXPOSE 1433 
> EXPOSE 29051
> 
> COPY bin/x64/debug /root/ ENTRYPOINT
> /root/RmsMainConsole.exe

I CD into directory where my dockerfile is at and execute docker build. Error:

Docker CLI command : docker build -t rmsmainconsole:self-hosted .

Sending build context to Docker daemon  55.61MB
Step 1/6 : FROM microsoft/windowsservercore:ltsc2016
 ---> 9dbf7f740334
Step 2/6 : EXPOSE 80
 ---> Using cache
 ---> ad0ad85fd107
Step 3/6 : EXPOSE 1433
 ---> Using cache
 ---> 81ba13dbd4d4
Step 4/6 : EXPOSE 29051
 ---> Using cache
 ---> 1fa3db800abf
Step 5/6 : COPY bin/x64/debug /root/
COPY failed: CreateFile \\?\C:\ProgramData\Docker\tmp\docker-builder043346063\bin\x64\debug: The system cannot find the path specified.

You can see that PATH couldn't be found. Whereas i tried to create docker file on my .sln level. I changed one line in my docker file.

COPY RmsMainConsole/bin/x64/debug /root/

Note: "RmsMainConsole" directory has been added.

i executed the docker build at my .sln level and i built it successfully. Logs are:

Sending build context to Docker daemon   1.15GB
Step 1/6 : FROM microsoft/windowsservercore:ltsc2016
 ---> 9dbf7f740334
Step 2/6 : EXPOSE 80
 ---> Running in fe97cf236d5a
Removing intermediate container fe97cf236d5a
 ---> c31e236353b6
Step 3/6 : EXPOSE 1433
 ---> Running in f031fce5ecba
Removing intermediate container f031fce5ecba
 ---> 96c704c68ffb
Step 4/6 : EXPOSE 29051
 ---> Running in 365e2be43d0e
Removing intermediate container 365e2be43d0e
 ---> d30c3fb2214b
Step 5/6 : COPY RmsMainConsole/bin/x64/debug /root/
 ---> b214c1edc256
Step 6/6 : ENTRYPOINT /root/RmsMainConsole.exe
 ---> Running in 5c819915532a
Removing intermediate container 5c819915532a
 ---> 247f01bb9b82
Successfully built 247f01bb9b82
Successfully tagged rmsmainconsole:self-hosted

I noticed two difference between the successful and failed build: 1. Size on the docker context 2. The logs at step 5/6:

COPY failed: CreateFile \?\C:\ProgramData\Docker\tmp\docker-builder043346063\bin\x64\debug: The system cannot find the path specified.

and

---> b214c1edc256

How should i use visual studio docker support to build my docker image. Where did i go wrong ?

Answer 1

Not sure, whether I answer your question - first or second :).

I was also wondering how Visual Studio is using Docker, because Dockerfile is created within project folder, but it contains paths for COPY like it was in the root (sln) folder.

I played with it a bit and answer is pretty simple.

Visual Studio builds images from the solution folder using -f switch to point to Dockerfile. You can watch Output window to see it running following command:

docker build -f "<path to Dockerfile>" -t <name:tag> --target base  --label "com.microsoft.created-by=visual-studio" "<solution dir>"

So, I would recommend having Dockerfile in project folder and run it from the root folder using -f option like Visual Studio does it.

Does it answer your question(s)?

Answer 2

I think the actual reason for this is much simpler. If you look at the docker ignore (.dockerignore) file, you'll notice that it ignores everything except for a couple of obj folders. Try removing the * at the top of the docker ignore file to test this out. Then you can selectively ignore things you have in the project folder that you'd like to copy over. I ran into this as well and it took lots of trial and error before I thought to look at the ignore file.