Docker image with lldb debugger and SOS plugin, compiled from sources with lldb headers. By default loads process coredump from /tmp/coredump, loads SOS plugin and prints current exception, leaving lldb shell open. Image tag matches dotnet runtime version.

docker run --rm -it -v /stripe/upload/coredump:/tmp/coredump 6opuc/lldb-netcore

• /stripe/upload/coredump - Path to coredump of crashed process on docker host machine

1. Copy crashed process working directory(coredump is automatically created in crashed process working directory) to temporary directory on host:

docker cp 79686a7aff63:/app /tmp

• 79686a7aff63 - id of container with crashed process
• /app - crashed process working directory inside container filesystem

2. Find crashed process coredump:

ls /tmp/app/core.*

example output:

/tmp/app/core.26939

3. Open coredump with debugger:

docker run --rm -it -v /tmp/app/core.26939:/tmp/coredump 6opuc/lldb-netcore

example output:

(lldb) target create "/usr/bin/dotnet" --core "/tmp/coredump"
Core file '/tmp/coredump' (x86_64) was loaded.
(lldb) plugin load /coreclr/libsosplugin.so
(lldb) sos PrintException
Exception object: 00007f3fb001ce08
Exception type:   System.NullReferenceException
Message:          Object reference not set to an instance of an object.
InnerException:   <none>
StackTrace (generated):
    SP               IP               Function
    00007FFCE0A312F0 00007F3FD7940481 test.dll!test.Program.Main(System.String[])+0x1
StackTraceString: <none>
HResult: 80004003
(lldb)

4. Continue exploring coredump in lldb shell:

help

1. Get id of docker container(docker ps) you need to analyze. In this example it is "b5063ef5787c"

2. Run container with createdump utility(it needs sys_admin and sys_ptrace privileges. If your running container already has these privileges you can attach to running container and run createdump utility from there):

docker run --rm -it --cap-add sys_admin --cap-add sys_ptrace --net=container:b5063ef5787c --pid=container:b5063ef5787c -v /tmp:/tmp 6opuc/lldb-netcore /bin/bash

• b5063ef5787c - id of container you need to analyze
• /tmp - temporary directory on host, where coredump will be created

3. Find PID of dotnet process you need to analyze:

ps aux

In this example PID is "7"

4. Create coredump of dotnet process and exit from container:

createdump -u -f /tmp/coredump 7
exit

• 7 is dotnet process PID

5. Open coredump with debugger:

docker run --rm -it -v /tmp/coredump:/tmp/coredump 6opuc/lldb-netcore

example output:

(lldb) target create "/usr/bin/dotnet" --core "/tmp/coredump"
Core file '/tmp/coredump' (x86_64) was loaded.
(lldb) plugin load /coreclr/libsosplugin.so
(lldb) sos PrintException
There is no current managed exception on this thread
(lldb)

6. Continue exploring coredump in lldb shell:

help

docker build \
	--tag 6opuc/lldb-netcore:2.2.3 \
   	--build-arg BASE_IMAGE=mcr.microsoft.com/dotnet/core/sdk:2.2.105 \
   	--build-arg CORECLR_BRANCH=v2.2.3 \
	.

docker build \
	--tag 6opuc/lldb-netcore:2.2.2 \
   	--build-arg BASE_IMAGE=mcr.microsoft.com/dotnet/core/sdk:2.2.104 \
   	--build-arg CORECLR_BRANCH=v2.2.2 \
	.

docker build \
	--tag 6opuc/lldb-netcore:2.1.8 \
	--build-arg BASE_IMAGE=mcr.microsoft.com/dotnet/core/sdk:2.1.504 \
   	--build-arg CORECLR_BRANCH=v2.1.8 \
	.

docker build \
	--tag 6opuc/lldb-netcore:2.0.3 \
	--build-arg BASE_IMAGE=microsoft/dotnet:2.0.3-sdk \
	--build-arg CORECLR_BRANCH=v2.0.3 \
	.

• BASE_IMAGE - Base image of dotnet sdk. Used both at build time and runtime.
• CORECLR_BRANCH - coreclr repository(https://github.com/dotnet/coreclr.git) branch/tag to build SOS plugin from