Updates on a file in host system will NOT be reflected in container, when bind mount is below /System/Volumes/Data

[JochenHiller]

Description

Updates on a file will not be reflected in container.

It will only fail, when the filesystem is below the /System/Volumes/Data folder.
It does work well when filesystem is below /Users/username, /Volumes/Data.

I am quite sure that this did work 1-2 years ago, when using Apple Hypervisor and VirtioFS with directories below /System/Volumes/Data.

macOS 26.2 (25C56), APFS (Encrypted)

Reproduce

# macOS
cd /System/Volumes/Data
sudo mkdir docker-test
sudo chown <my-user> docker-test
cd docker-test
mkdir directory
echo "123" >directory/test.txt

# add /System/Volumes/Data/docker-test as file-sharing resource to Docker
docker run -it -w /var/workdir --mount type=bind,source="/System/Volumes/Data/docker-test",target=/var/workdir --rm alpine sh
/var/workdir # cat directory/test.txt
123

# now change file in another host console: append 456
echo "456" >>directory/test.txt

# now check again file in container, no update visible
/var/workdir # cat directory/test.txt
111

# now change file in another host console: add 789 in vi
vi directory/test.txt

# now check again file in container, error
/var/workdir # cat directory/test.txt
cat: can't open 'directory/test.txt': No such file or directory
# check directory
/var/workdir # ls -al directory/
total 4
drwxr-xr-x    3 root     root            96 Jan 26 11:05 .
drwxr-xr-x    2 root     root            64 Jan 26 10:59 ..
-rw-r--r--    1 root     root            16 Jan 26 11:05 test.txt
# now check again file in container, all updates visible
/var/workdir # cat directory/test.txt 
123
456
789

Expected behavior

File update should be visible in container immediately.

docker version

Client:
 Version:           29.1.3
 API version:       1.52
 Go version:        go1.25.5
 Git commit:        f52814d
 Built:             Fri Dec 12 14:48:46 2025
 OS/Arch:           darwin/arm64
 Context:           desktop-linux

Server: Docker Desktop 4.57.0 (215387)
 Engine:
  Version:          29.1.3
  API version:      1.52 (minimum version 1.44)
  Go version:       go1.25.5
  Git commit:       fbf3ed2
  Built:            Fri Dec 12 14:50:40 2025
  OS/Arch:          linux/arm64
  Experimental:     false
 containerd:
  Version:          v2.2.1
  GitCommit:        dea7da592f5d1d2b7755e3a161be07f43fad8f75
 runc:
  Version:          1.3.4
  GitCommit:        v1.3.4-0-gd6d73eb8
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

docker info

Client:
 Version:    29.1.3
 Context:    desktop-linux
 Debug Mode: false
 Plugins:
  ai: Docker AI Agent - Ask Gordon (Docker Inc.)
    Version:  v1.17.1
    Path:     /Users/username/.docker/cli-plugins/docker-ai
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.30.1-desktop.1
    Path:     /Users/username/.docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v5.0.1
    Path:     /Users/username/.docker/cli-plugins/docker-compose
  debug: Get a shell into any image or container (Docker Inc.)
    Version:  0.0.47
    Path:     /Users/username/.docker/cli-plugins/docker-debug
  desktop: Docker Desktop commands (Docker Inc.)
    Version:  v0.2.0
    Path:     /Users/username/.docker/cli-plugins/docker-desktop
  extension: Manages Docker extensions (Docker Inc.)
    Version:  v0.2.31
    Path:     /Users/username/.docker/cli-plugins/docker-extension
  init: Creates Docker-related starter files for your project (Docker Inc.)
    Version:  v1.4.0
    Path:     /Users/username/.docker/cli-plugins/docker-init
  mcp: Docker MCP Plugin (Docker Inc.)
    Version:  v0.35.0
    Path:     /Users/username/.docker/cli-plugins/docker-mcp
  model: Docker Model Runner (Docker Inc.)
    Version:  v1.0.6
    Path:     /Users/username/.docker/cli-plugins/docker-model
  offload: Docker Offload (Docker Inc.)
    Version:  v0.5.40
    Path:     /Users/username/.docker/cli-plugins/docker-offload
  pass: Docker Pass Secrets Manager Plugin (beta) (Docker Inc.)
    Version:  v0.0.22
    Path:     /Users/username/.docker/cli-plugins/docker-pass
  sandbox: Docker Sandbox (Docker Inc.)
    Version:  v0.6.0
    Path:     /Users/username/.docker/cli-plugins/docker-sandbox
  sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc.)
    Version:  0.6.0
    Path:     /Users/username/.docker/cli-plugins/docker-sbom
  scout: Docker Scout (Docker Inc.)
    Version:  v1.19.0
    Path:     /Users/username/.docker/cli-plugins/docker-scout

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 1
 Server Version: 29.1.3
 Storage Driver: overlayfs
  driver-type: io.containerd.snapshotter.v1
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: dea7da592f5d1d2b7755e3a161be07f43fad8f75
 runc version: v1.3.4-0-gd6d73eb8
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.12.54-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: aarch64
 CPUs: 10
 Total Memory: 7.653GiB
 Name: docker-desktop
 ID: c1f54a72-46a9-4ebb-afe3-5686ebca1111
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Labels:
  com.docker.desktop.address=unix:///Users/username/Library/Containers/com.docker.docker/Data/docker-cli.sock
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5555
  127.0.0.0/8
  ::1/128
 Live Restore Enabled: false

Diagnostics ID

238F29B6-D7EC-45F6-9094-A03DB8FCD1E1/20260126120023

Additional Info

Meanwhile I switched to podman, where file synchronisation does work well even when filesystem is below /System/Volumes/Data.