Volume mounting issues with Docker-in-Docker in GitLab Runner Kubernetes executor

Question

Problem Summary I'm running a GitLab CI pipeline with a Kubernetes runner that uses Docker-in-Docker (privileged mode). When I try to mount a volume from the GitLab Runner's filesystem into a Docker container, the files exist on the host but are not accessible inside the container. Environment GitLab Runner: Kubernetes executor with privileged mode Docker: Running in privileged container with Docker socket mounted GitLab Runner Config:

config: |
 [[runners]]
 id = 0
 output_limit = 100000
 [runners.kubernetes]
 namespace = "{{.Release.Namespace}}"
 image_pull_secrets = ["my-registry-secret"]
 memory_request = "1048Mi"
 cpu_request = "500m"
 logs_section_max_size = 52428800 # 50 MB
 timeout = 3600
 privileged = true
 helper_cpu_request = "500m"
 helper_memory_request = "168Mi"
 helper_image = "docker.io/gitlab/gitlab-runner-helper:x86_64-v17.0.0"
 pull_policy = "if-not-present"
 image = "xxxxxxxxxxxxxx"
 # Enable shared storage for docker in docker
 builds_dir = "/builds"
 cache_dir = "/cache" 
 [runners.kubernetes.volumes]
 [[runners.kubernetes.volumes.host_path]]
 name = "docker"
 mount_path = "/var/run/docker.sock"
 read_only = false
 host_path = "/var/run/docker.sock"
 [[runners.kubernetes.volumes.host_path]]
 name = "cache"
 mount_path = "/cache"
 read_only = false
 host_path = "/tmp/cache"
 [[runners.kubernetes.volumes.host_path]]
 name = "builds"
 mount_path = "/builds"
 read_only = false
 host_path = "/tmp/gitlab-runner/builds"
 [[runners.kubernetes.volumes.host_path]]
 name = "runner-secrets"
 mount_path = "/etc/gitlab-runner/certs"
 read_only = true
 host_path = "/etc/ssl/certs"

Current Code

container_monorepo_path = "/workspace"
 docker_command = (
 f'docker run --rm '
 f'-v {monorepo_root}:{container_monorepo_path} '
 f'-w {container_monorepo_path}/{relative_project_path} '
 f'--user root '
 f'private-registry.company.com/docker-adv-all/docker-agent-playwright '
 f'sh -c "'
 f'npm config set strict-ssl false && '
 f'npm install -g pnpm nx && '
 f'pnpm nx run {project_name}:{task}"'
 )

Actual Error Output

[2025年07月11日 22:24:36] - [INFO]: running command => docker run --rm -v /builds/t3_zrKwM/0/550016304/cp-monorepo:/workspace -w /workspace/packages/frontend/actions --user root private-registry.company.com/docker-agent-playwright:latest sh -c "npm config set strict-ssl false && npm install -g pnpm nx && pnpm nx run actions:test-component"
[2025年07月11日 22:24:46] - [INFO]: added 125 packages in 9s
[2025年07月11日 22:24:46] - [INFO]: 28 packages are looking for funding
[2025年07月11日 22:24:46] - [INFO]: run `npm fund` for details
[2025年07月11日 22:24:46] - [ERROR]: npm notice
[2025年07月11日 22:24:46] - [ERROR]: npm notice New major version of npm available! 9.5.1 -> 11.4.2
[2025年07月11日 22:24:46] - [ERROR]: npm notice Changelog: <https://github.com/npm/cli/releases/tag/v11.4.2>
[2025年07月11日 22:24:46] - [ERROR]: npm notice Run `npm install -g [email protected]` to update!
[2025年07月11日 22:24:46] - [ERROR]: npm notice
[2025年07月11日 22:24:46] - [INFO]: ERR_PNPM_NO_IMPORTER_MANIFEST_FOUND No package.json (or package.yaml, or package.json5) was found in "/workspace/packages/frontend/actions".
[2025年07月11日 22:24:47] - [ERROR]: ❌ test-component failed