Windows docker container buildctl does not allow mounting secrets. It fails mounting to linux tmpfs location

[lorentz-1]

I am using version 1.7.18 of containerd and 0.14.0 of buildkit.
When creating a docker image from docker file using the following command

buildctl.exe build
--frontend dockerfile.v0
--local context=.
--local dockerfile=.
--output type=image,\"name=test_image:1.0\"
--secret id=creds-usr,env=CREDS_USR
--secret id=creds-psw,env=CREDS_PSW
${buildArgs.join(' ')}

---

I have the following dockerfile

FROM mcr.microsoft.com/windows/servercore
RUN --mount=type=secret,id=creds-usr,required=True,target=C:\secrets\creds-usr
--mount=type=secret,id=creds-psw,required=True,target=C:\secrets\creds-psw
//Followed by other commands I use to perform network operations.

---

The build output fails at following error
unable to setup secret mount: invalid windows mount type: 'tmpfs'

Has any one has success is mounting secrets using windows containers?

Originally posted by @lorentz-1 in #5272

[jia6214876]

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[lilayam]

I encountered this bug. Was hoping someone would fix it or propose some ways to fix this

[profnandaa]

Currently RUN --mount is not supported on Windows. Current mount types are Linux specific, like tmpfs.
We are yet to look into the design of this feature but it's good to see that there's demand for it, so this will help in our prioritization.

However, currently, the aim is to have full parity with the classic builder (current docker build for Windows) first.

[profnandaa]

UPDATE: currently looking into this, see #5678

[iancward]

@profnandaa is the limitation in buildkit or in buildctl? Would using docker build with buildkit on windows be a workaround? Or can you not even use docker build with buildkit?

[profnandaa]

@iancward -- this is a limitation currently, and we have it on our backlog as one of the feature-parity gaps that we need to close. Currently, secret mounts are being provisioned through tmpfs, which is a Linux-only feature. We are considering some alternatives on the Windows side but are not straightforward.

On your other question about docker with buildkit -- this is yet to be enabled for WCOW but it's on the roadmap too.