Windows + VS Code + WSL + Docker

[agroszer]

Environment data

• debugpy version: 1.8.16
• OS and version: windows 11 23H2 WSL 2.5.10 ubuntu 22.04
• Python version (& distribution if applicable, e.g. Anaconda): 3.11.13
• Using VS Code or Visual Studio: VS Code 1.102.3

Actual behavior

VS Code running on windows, attached to WSL
app/script running in WSL in a docker container
AFAICS port 5678 is exposed to WSL from the container

VS Code fails to connect

Expected behavior

VS Code debugger connects fine

Steps to reproduce:

I shall have a pretty standard launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python Debugger: Remote Attach",
            "type": "debugpy",
            "request": "attach",
            "connect": {
                "host": "localhost",
                "port": 5678
            },
            "pathMappings": [
                {
                    "localRoot": "${workspaceFolder}",
                    "remoteRoot": "."
                }
            ],
            "logToFile": true
        }
    ]
}

Clicking the start debugging button scrolls the progress a bit then nothing happens
The Debugpy Attacher extension outputs a warning like debug session failed to start

The log shows:

0 Starting Session:
{
    "name": "Python Debugger: Remote Attach",
    "type": "debugpy",
    "request": "attach",
    "connect": {
        "host": "localhost",
        "port": 5678
    },
    "pathMappings": [
        {
            "localRoot": "/home/a/app",
            "remoteRoot": "."
        }
    ],
    "logToFile": true,
    "__configurationTarget": 6,
    "clientOS": "unix",
    "debugOptions": [
        "RedirectOutput",
        "ShowReturnValue"
    ],
    "justMyCode": false,
    "showReturnValue": true,
    "workspaceFolder": "/home/a/app"
}
3 Error:
{}
7 Client --> Adapter:
{
    "command": "disconnect",
    "arguments": {
        "restart": false
    },
    "type": "request",
    "seq": 1
}
7 Client --> Adapter:
{
    "command": "initialize",
    "arguments": {
        "clientID": "vscode",
        "clientName": "Visual Studio Code",
        "adapterID": "debugpy",
        "pathFormat": "path",
        "linesStartAt1": true,
        "columnsStartAt1": true,
        "supportsVariableType": true,
        "supportsVariablePaging": true,
        "supportsRunInTerminalRequest": true,
        "locale": "en",
        "supportsProgressReporting": true,
        "supportsInvalidatedEvent": true,
        "supportsMemoryReferences": true,
        "supportsArgsCanBeInterpretedByShell": true,
        "supportsMemoryEvent": true,
        "supportsStartDebuggingRequest": true,
        "supportsANSIStyling": true
    },
    "type": "request",
    "seq": 2
}
718 Stopping Session

When I try to run attach with debugpy in the very same container with:

./ve/bin/debugpy --connect 5678 --log-to-stderr ./bin/test

I get:

...
D+00000.207: connect(('127.0.0.1', 5678), **{'access_token': None, 'parent_session_pid': None})

I+00000.207: Initial debug configuration: {
                 "qt": "none",
                 "subProcess": true,
                 "python": "/code/ve/bin/python3.11",
                 "pythonEnv": {}
             }

D+00000.207: pydevd.settrace(*(), **{'host': '127.0.0.1', 'port': 5678, 'client_access_token': None, 'ppid': 0, 'suspend': False, 'patch_multiprocessing': True, 'dont_trace_start_patterns': ('/code/ve/lib/python3.11/site-packages/debugpy',), 'dont_trace_end_patterns': ('debugpy_launcher.py',)})

Traceback (most recent call last):
  File "/code/ve/lib/python3.11/site-packages/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_comm.py", line 275, in _on_run
    self.process_net_command_json(self.py_db, json_contents)
  File "/code/ve/lib/python3.11/site-packages/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_process_net_command_json.py", line 197, in process_net_command_json
    assert request.type == "request"
           ^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError

What's wrong? How to debug?

[rchiodo]

Can you check the Debug console output in VS code when attaching?

Mine shows this on a default docker container:

Attaching to PID: 1147 (elapsed: 1.01s).
Attach to PID failed.
--- Starting attach to pid: 1147 ---
0.01s - Debugger warning: It seems that frozen modules are being used, which may
0.00s - make the debugger miss breakpoints. Please pass -Xfrozen_modules=off
0.00s - to python to disable frozen modules.
0.00s - Note: Debugging will proceed. Set PYDEVD_DISABLE_FILE_VALIDATION=1 to disable this validation.
/bin/sh: 1: gdb: not found
E+00000.112: Code injection into PID=1147 failed:
             
             Traceback (most recent call last):
               File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/server/cli.py", line 461, in attach_to_pid
                 add_code_to_python_process.run_python_code(
               File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/_vendored/pydevd/pydevd_attach_to_process/add_code_to_python_process.py", line 480, in run_python_code_linux
                 subprocess.check_call(" ".join(cmd), shell=True, env=env)
               File "/usr/local/lib/python3.12/subprocess.py", line 413, in check_call
                 raise CalledProcessError(retcode, cmd)
             subprocess.CalledProcessError: Command 'gdb --nw --nh --nx --pid 1147 --batch --eval-command='set scheduler-locking off' --eval-command='set architecture auto' --eval-command='call (void*)dlopen("/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/_vendored/pydevd/pydevd_attach_to_process/attach_linux_amd64.so", 2)' --eval-command='sharedlibrary attach_linux_amd64' --eval-command='call (int)DoAttach(0, "import codecs;import json;import sys;decode = lambda s: codecs.utf_8_decode(bytearray(s))[0] if s is not None else None;script_dir = decode([47, 104, 111, 109, 101, 47, 118, 115, 99, 111, 100, 101, 47, 46, 118, 115, 99, 111, 100, 101, 45, 115, 101, 114, 118, 101, 114, 47, 101, 120, 116, 101, 110, 115, 105, 111, 110, 115, 47, 109, 115, 45, 112, 121, 116, 104, 111, 110, 46, 100, 101, 98, 117, 103, 112, 121, 45, 50, 48, 50, 53, 46, 49, 48, 46, 48, 47, 98, 117, 110, 100, 108, 101, 100, 47, 108, 105, 98, 115, 47, 100, 101, 98, 117, 103, 112, 121, 47, 97, 100, 97, 112, 116, 101, 114, 47, 46, 46, 47, 46, 46, 47, 100, 101, 98, 117, 103, 112, 121, 47, 46, 46, 47, 100, 101, 98, 117, 103, 112, 121, 47, 115, 101, 114, 118, 101, 114]);setup = json.loads(decode([123, 34, 109, 111, 100, 101, 34, 58, 32, 34, 99, 111, 110, 110, 101, 99, 116, 34, 44, 32, 34, 97, 100, 100, 114, 101, 115, 115, 34, 58, 32, 91, 34, 49, 50, 55, 46, 48, 46, 48, 46, 49, 34, 44, 32, 53, 51, 54, 50, 57, 93, 44, 32, 34, 119, 97, 105, 116, 95, 102, 111, 114, 95, 99, 108, 105, 101, 110, 116, 34, 58, 32, 102, 97, 108, 115, 101, 44, 32, 34, 108, 111, 103, 95, 116, 111, 34, 58, 32, 110, 117, 108, 108, 44, 32, 34, 97, 100, 97, 112, 116, 101, 114, 95, 97, 99, 99, 101, 115, 115, 95, 116, 111, 107, 101, 110, 34, 58, 32, 34, 98, 50, 49, 57, 49, 98, 102, 50, 57, 48, 52, 48, 102, 50, 98, 55, 50, 55, 50, 48, 55, 97, 100, 48, 53, 50, 98, 97, 97, 100, 98, 56, 102, 52, 97, 101, 57, 50, 102, 54, 52, 48, 100, 102, 49, 49, 102, 49, 52, 52, 49, 102, 98, 52, 51, 53, 99, 99, 50, 55, 100, 100, 57, 48, 34, 125]));sys.path.insert(0, script_dir);import attach_pid_injected;del sys.path[0];attach_pid_injected.attach(setup);", 0)'' returned non-zero exit status 127.
             
             Stack where logged:
               File "<frozen runpy>", line 198, in _run_module_as_main
               File "<frozen runpy>", line 88, in _run_code
               File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/__main__.py", line 71, in <module>
                 cli.main()
               File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/server/cli.py", line 501, in main
                 run()
               File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/server/cli.py", line 468, in attach_to_pid
                 log.reraise_exception("Code injection into PID={0} failed:", pid)
               File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/common/log.py", line 222, in reraise_exception
                 _exception(format_string, *args, **kwargs)
             

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/__main__.py", line 71, in <module>
    cli.main()
  File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/server/cli.py", line 501, in main
    run()
  File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/server/cli.py", line 468, in attach_to_pid
    log.reraise_exception("Code injection into PID={0} failed:", pid)
  File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/adapter/../../debugpy/../debugpy/server/cli.py", line 461, in attach_to_pid
    add_code_to_python_process.run_python_code(
  File "/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/_vendored/pydevd/pydevd_attach_to_process/add_code_to_python_process.py", line 480, in run_python_code_linux
    subprocess.check_call(" ".join(cmd), shell=True, env=env)
  File "/usr/local/lib/python3.12/subprocess.py", line 413, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'gdb --nw --nh --nx --pid 1147 --batch --eval-command='set scheduler-locking off' --eval-command='set architecture auto' --eval-command='call (void*)dlopen("/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/_vendored/pydevd/pydevd_attach_to_process/attach_linux_amd64.so", 2)' --eval-command='sharedlibrary attach_linux_amd64' --eval-command='call (int)DoAttach(0, "import codecs;import json;import sys;decode = lambda s: codecs.utf_8_decode(bytearray(s))[0] if s is not None else None;script_dir = decode([47, 104, 111, 109, 101, 47, 118, 115, 99, 111, 100, 101, 47, 46, 118, 115, 99, 111, 100, 101, 45, 115, 101, 114, 118, 101, 114, 47, 101, 120, 116, 101, 110, 115, 105, 111, 110, 115, 47, 109, 115, 45, 112, 121, 116, 104, 111, 110, 46, 100, 101, 98, 117, 103, 112, 121, 45, 50, 48, 50, 53, 46, 49, 48, 46, 48, 47, 98, 117, 110, 100, 108, 101, 100, 47, 108, 105, 98, 115, 47, 100, 101, 98, 117, 103, 112, 121, 47, 97, 100, 97, 112, 116, 101, 114, 47, 46, 46, 47, 46, 46, 47, 100, 101, 98, 117, 103, 112, 121, 47, 46, 46, 47, 100, 101, 98, 117, 103, 112, 121, 47, 115, 101, 114, 118, 101, 114]);setup = json.loads(decode([123, 34, 109, 111, 100, 101, 34, 58, 32, 34, 99, 111, 110, 110, 101, 99, 116, 34, 44, 32, 34, 97, 100, 100, 114, 101, 115, 115, 34, 58, 32, 91, 34, 49, 50, 55, 46, 48, 46, 48, 46, 49, 34, 44, 32, 53, 51, 54, 50, 57, 93, 44, 32, 34, 119, 97, 105, 116, 95, 102, 111, 114, 95, 99, 108, 105, 101, 110, 116, 34, 58, 32, 102, 97, 108, 115, 101, 44, 32, 34, 108, 111, 103, 95, 116, 111, 34, 58, 32, 110, 117, 108, 108, 44, 32, 34, 97, 100, 97, 112, 116, 101, 114, 95, 97, 99, 99, 101, 115, 115, 95, 116, 111, 107, 101, 110, 34, 58, 32, 34, 98, 50, 49, 57, 49, 98, 102, 50, 57, 48, 52, 48, 102, 50, 98, 55, 50, 55, 50, 48, 55, 97, 100, 48, 53, 50, 98, 97, 97, 100, 98, 56, 102, 52, 97, 101, 57, 50, 102, 54, 52, 48, 100, 102, 49, 49, 102, 49, 52, 52, 49, 102, 98, 52, 51, 53, 99, 99, 50, 55, 100, 100, 57, 48, 34, 125]));sys.path.insert(0, script_dir);import attach_pid_injected;del sys.path[0];attach_pid_injected.attach(setup);", 0)'' returned non-zero exit status 127.
PYDEVD_GDB_SCAN_SHARED_LIBRARIES not set (scanning all libraries for needed symbols).
Running: gdb --nw --nh --nx --pid 1147 --batch --eval-command='set scheduler-locking off' --eval-command='set architecture auto' --eval-command='call (void*)dlopen("/home/vscode/.vscode-server/extensions/ms-python.debugpy-2025.10.0/bundled/libs/debugpy/_vendored/pydevd/pydevd_attach_to_process/attach_linux_amd64.so", 2)' --eval-command='sharedlibrary attach_linux_amd64' --eval-command='call (int)DoAttach(0, "import codecs;import json;import sys;decode = lambda s: codecs.utf_8_decode(bytearray(s))[0] if s is not None else None;script_dir = decode([47, 104, 111, 109, 101, 47, 118, 115, 99, 111, 100, 101, 47, 46, 118, 115, 99, 111, 100, 101, 45, 115, 101, 114, 118, 101, 114, 47, 101, 120, 116, 101, 110, 115, 105, 111, 110, 115, 47, 109, 115, 45, 112, 121, 116, 104, 111, 110, 46, 100, 101, 98, 117, 103, 112, 121, 45, 50, 48, 50, 53, 46, 49, 48, 46, 48, 47, 98, 117, 110, 100, 108, 101, 100, 47, 108, 105, 98, 115, 47, 100, 101, 98, 117, 103, 112, 121, 47, 97, 100, 97, 112, 116, 101, 114, 47, 46, 46, 47, 46, 46, 47, 100, 101, 98, 117, 103, 112, 121, 47, 46, 46, 47, 100, 101, 98, 117, 103, 112, 121, 47, 115, 101, 114, 118, 101, 114]);setup = json.loads(decode([123, 34, 109, 111, 100, 101, 34, 58, 32, 34, 99, 111, 110, 110, 101, 99, 116, 34, 44, 32, 34, 97, 100, 100, 114, 101, 115, 115, 34, 58, 32, 91, 34, 49, 50, 55, 46, 48, 46, 48, 46, 49, 34, 44, 32, 53, 51, 54, 50, 57, 93, 44, 32, 34, 119, 97, 105, 116, 95, 102, 111, 114, 95, 99, 108, 105, 101, 110, 116, 34, 58, 32, 102, 97, 108, 115, 101, 44, 32, 34, 108, 111, 103, 95, 116, 111, 34, 58, 32, 110, 117, 108, 108, 44, 32, 34, 97, 100, 97, 112, 116, 101, 114, 95, 97, 99, 99, 101, 115, 115, 95, 116, 111, 107, 101, 110, 34, 58, 32, 34, 98, 50, 49, 57, 49, 98, 102, 50, 57, 48, 52, 48, 102, 50, 98, 55, 50, 55, 50, 48, 55, 97, 100, 48, 53, 50, 98, 97, 97, 100, 98, 56, 102, 52, 97, 101, 57, 50, 102, 54, 52, 48, 100, 102, 49, 49, 102, 49, 52, 52, 49, 102, 98, 52, 51, 53, 99, 99, 50, 55, 100, 100, 57, 48, 34, 125]));sys.path.insert(0, script_dir);import attach_pid_injected;del sys.path[0];attach_pid_injected.attach(setup);", 0)'

This is because GDB is required for attach on linux.

[rchiodo]

I got this to work in a devcontainer by doing the following:

Adding this to the Dockerfile:

RUN apt-get update && \
    apt-get install -y gdb && \
    apt-get clean

Adding this to the devcontainer.json

    "runArgs": [
    "--cap-add=SYS_PTRACE",
    "--security-opt=seccomp=unconfined",
    "--privileged"
      ],
    "forwardPorts": [5678],
    "postCreateCommand": "echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope",

[rchiodo]

Then I just used this launch.json:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python Debugger: Attach using Process Id",
            "type": "debugpy",
            "request": "attach",
            "processId": "${command:pickProcess}"
        }
    ]
}

And this app that I ran from the terminal:

import os
print(os.getpid())


while True:
    input('Hit enter to continue')
    print('After enter')

Debug console should output something like so when it works:

Attaching to PID: 1104 (elapsed: 1.00s).
Attaching to PID: 1104 (elapsed: 2.00s).
Attaching to PID: 1104 (elapsed: 3.00s).
Attaching to PID: 1104 (elapsed: 4.00s).
Attaching to PID: 1104 (elapsed: 5.00s).

[rchiodo]

I've added a wiki page that will helpfully help with this sort of thing in the future:
https://github.com/microsoft/debugpy/wiki/Debugging-inside-of-a-docker-container

[agroszer]

Hi,

I'm trying to use the debugger with:

...
        import debugpy

        # debugpy.listen(('host.docker.internal', 5678))
        debugpy.listen(5678)
        
        print("Waiting for debugger attach")
        debugpy.wait_for_client()
        debugpy.breakpoint()
        print('break on this line')
...

when I run the script I get:

0.00s - Debugger warning: It seems that frozen modules are being used, which may
0.00s - make the debugger miss breakpoints. Please pass -Xfrozen_modules=off
0.00s - to python to disable frozen modules.
0.00s - Note: Debugging will proceed. Set PYDEVD_DISABLE_FILE_VALIDATION=1 to disable this validation.
Waiting for debugger attach

VS code seems to want to start debugging but end up with the Unable to start session message

Do I really need gdb and ptrace to attach this way?

I have control over the code I want to debug, I can add any code...

[rchiodo]

That sounds more like the port isn't open. I don't believe you'd need ptrace if you're injecting debugpy yourself.

If you are controlling startup of the process, can you launch it from vscode?

[agroszer]

Phew, got it finally working

Things I did:

• WSL restarts (well it sometimes dies on it's own, also gets connection problems on sleep, even VS Code looses connection)
• container restarts
• ./ve/bin/debugpy --listen 0.0.0.0:5678 --wait-for-client --log-to-stderr ./bin/test started to work
• disabled DebugPy Attacher
• import debugpy; debugpy.listen(('0.0.0.0',5678)) started to work

But I think the key was using 0.0.0.0 to listen to.

FTR

export PYDEVD_DEBUG=True
export PYDEVD_DEBUG_FILE=.../pydevd.log 

before trying to listen will make pydevd log to the given file

VS Code logs go to ~/.vscode-server/extensions/ms-python.debugpy<version> on WSL, not on windows

[agroszer]

BTW, is there any way to turn this around? VS Code listening and debugpy.connect() ? I found references in docs for debugpy.connect() but nothing for the VS Code side.

The thing is we have more containers with python code and it will be a pain to setup debugging this way in all (at the same time).
Port 5678 can be mapped to a single container at the same time.
With Komodo IDE the solution was that the IDE was listening for connections and the client dbgp initiated the connection.

[rchiodo]

I don't believe VS Code has a way to listen. Not that I've seen at least. It does either attach or launch.

Glad you solved it though. Thanks for responding with what you did.