Unable to find fallback package folder '/usr/local/share/dotnet/sdk/NuGetFallbackFolder'.

[dvdnhm]

Steps to reproduce the issue

1. Get Docker file with core 3.1 references from the official source: https://github.com/dotnet/dotnet-docker/blob/master/samples/dotnetapp/Dockerfile
2. run docker build

Expected behavior

Builds works as expected.

Actual behavior

Step 7/11 : RUN dotnet publish -c release -o /app --no-restore
---> Running in d872ea0af9ca
Microsoft (R) Build Engine version 16.6.0+5ff7b0c9e for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: The "ResolvePackageAssets" task failed unexpectedly. [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: NuGet.Packaging.Core.PackagingException: Unable to find fallback package folder '/usr/local/share/dotnet/sdk/NuGetFallbackFolder'. [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at NuGet.Packaging.FallbackPackagePathResolver..ctor(String userPackageFolder, IEnumerable1 fallbackPackageFolders) [/source/api.csproj] /usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(IEnumerable1 packageFolders) [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(LockFile lockFile) [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheWriter..ctor(ResolvePackageAssets task) [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader.CreateReaderFromDisk(ResolvePackageAssets task, Byte[] settingsHash) [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader..ctor(ResolvePackageAssets task) [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.ResolvePackageAssets.ReadItemGroups() [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.ResolvePackageAssets.ExecuteCore() [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.NET.Build.Tasks.TaskBase.Execute() [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [/source/api.csproj]
/usr/share/dotnet/sdk/3.1.301/Sdks/Microsoft.NET.Sdk/targets/Microsoft.PackageDependencyResolution.targets(234,5): error MSB4018: at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask) [/source/api.csproj]
The command '/bin/sh -c dotnet publish -c release -o /app --no-restore' returned a non-zero code: 1

Output of docker version

Client: Docker Engine - Community
 Version:           19.03.8
 API version:       1.40
 Go version:        go1.12.17
 Git commit:        afacb8b
 Built:             Wed Mar 11 01:21:11 2020
 OS/Arch:           darwin/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.8
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.17
  Git commit:       afacb8b
  Built:            Wed Mar 11 01:29:16 2020
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.2.13
  GitCommit:        7ad184331fa3e55e52b890ea95e65ba581ae3429
 runc:
  Version:          1.0.0-rc10
  GitCommit:        dc9208a3303feef5b3839f4323d9beb36df0a9dd
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

Output of docker info

Client:
 Debug Mode: false

Server:
 Containers: 4
  Running: 0
  Paused: 0
  Stopped: 4
 Images: 66
 Server Version: 19.03.8
 Storage Driver: overlay2
  Backing Filesystem: <unknown>
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 7ad184331fa3e55e52b890ea95e65ba581ae3429
 runc version: dc9208a3303feef5b3839f4323d9beb36df0a9dd
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 4.19.76-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: x86_64
 CPUs: 4
 Total Memory: 1.944GiB
 Name: docker-desktop
 ID: T3PU:U3ZK:JK3P:R4IT:RDRI:U3KP:N3FB:QHCT:3IZ3:2CFD:AAJC:FKUQ
 Docker Root Dir: /var/lib/docker
 Debug Mode: true
  File Descriptors: 161
  Goroutines: 145
  System Time: 2020-07-02T15:44:47.5965769Z
  EventsListeners: 3
 HTTP Proxy: gateway.docker.internal:3128
 HTTPS Proxy: gateway.docker.internal:3129
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine

[dvdnhm]

sorry false alarm, here is the problem for future newbies:

I already build my project in the past on my computer (not within docker), so I had bin and obj folders and they were copied into build process. I added .dockerignore file and build was successful.

PS: I wish the error message was more helpful.