#17851 Unable to mount sandboxes to docker environment for docker-in-docker setup Issue created by chris-stetter Describe the bug I am trying to use the new environments feature to run a test in a docker container. I am running Pants itself in a docker container (VSCode devcontainer). Running the test fails:

vscode ➜ /workspaces/pants-2.15 (master ✗) $ ./pants test tests/example_test.py 
08:55:13.90 [ERROR] 1 Exception encountered:

Engine traceback:
  in `test` goal
  in Run Pytest - (environment:linux_docker, tests/example_test.py)

ProcessExecutionFailure: Process 'Extract environment variables from the Docker image python:3.8-bullseye' failed with exit code 126.
stdout:
OCI runtime exec failed: exec failed: unable to start container process: chdir to cwd ("/pants-sandbox/pants-sandbox-QvFrxo") set in config.json failed: no such file or directory: unknown

stderr:



Use `--keep-sandboxes=on_failure` to preserve the process chroot for inspection.

Check out the code here https://github.com/chris-stetter/pants-2.15. I think the reason is simply that the files that are being mounted to the docker test container are not present on the host, but only in my container where I am running Pants. I can fix it the following way:

vscode ➜ /workspaces/pants-2.15 (master ✗) $ git diff
diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index df25fb1..c2b48aa 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -1,7 +1,8 @@
 {
        "name": "Python 3",
        "image": "<http://mcr.microsoft.com/vscode/devcontainers/python:3.8-bullseye|mcr.microsoft.com/vscode/devcontainers/python:3.8-bullseye>",
-       "mounts": ["source=/var/run/docker.sock,target=/var/run/docker.sock,type=bind,consistency=cached"],
+       "mounts": ["source=/var/run/docker.sock,target=/var/run/docker.sock,type=bind,consistency=cached",
+                          "source=/tmp,target=/tmp,type=bind,consistency=cached"],
 
        // Configure tool-specific properties.
        "customizations": {
diff --git a/pants.toml b/pants.toml
index 326451d..b801c98 100644
--- a/pants.toml
+++ b/pants.toml
@@ -1,5 +1,6 @@
 [GLOBAL]
 pants_version = "2.15.0rc0"
+named_caches_dir = "/tmp/named_caches"
 
 backend_packages = [
   'pants.backend.python',

That way, all files are also present on the host file system. Pants version 2.15.0rc0 OS Linux Additional info Should something like this be added to the docs? pantsbuild/pants