Docker on Windows using WSL daemon does not print exec output

Description

Running docker exec against a container running on the WSL Docker daemon returns no output.
Adding -i fixes the problem when running in an interactive PowerShell session.
However, when running in an environment with no stdin (like an Azure DevOps pipeline), even -i does not fix the output.

Related issues/PRs:

• https://github.com/docker/cli/issues/3586
• https://github.com/docker/cli/pull/4548
• https://github.com/golang/go/issues/35892#issuecomment-2568283851
• https://go-review.googlesource.com/c/go/+/637939

Reproduce

Using Windows Server 2022 with Docker Engine (not Desktop) installed, but should reproduce on any modern Windows OS with a Docker client.

1. Install Docker in WSL and expose a TCP port.

   # In WSL Bash
   curl -fsSL https://get.docker.com -o get-docker.sh
   ./get-docker.sh
   mkdir -p /etc/systemd/system/docker.service.d
   cat <<EOF > /etc/systemd/system/docker.service.d/docker.conf
   [Service]
   ExecStart=
   ExecStart=/usr/bin/dockerd
   EOF
   cat <<EOF > /etc/docker/daemon.json
   {
       "hosts": ["unix:///var/run/docker.sock", "tcp://0.0.0.0:2375"],
       "tls": false
   }
   EOF
   systemctl daemon-reload
   systemctl restart docker
   

2. In the Windows Docker client (running via PowerShell), add a context for WSL using the TCP port.

   # In PowerShell (all remaining steps as well)
   docker context create wsl --docker "host=tcp://localhost:2375"
   docker context use wsl
   

3. Create a Linux container in WSL Docker using the Windows Docker client.

   docker -c wsl run --rm -d --name linux-container mcr.microsoft.com/azurelinux/base/core:3.0 tail -f /dev/null
   

4. Create a Windows container as well.

   docker -c default run --rm -d --name windows-container mcr.microsoft.com/windows/nanoserver:ltsc2022 cmd /c ping -t localhost > NUL
   

5. Run a command in the Linux container (these will return no output).

   docker -c wsl exec linux-container cat /etc/os-release
   $null | docker -c wsl exec linux-container cat /etc/os-release
   $null | docker -c wsl exec -i linux-container cat /etc/os-release
   

6. Run a command in the Linux container (this will return output).

   docker -c wsl exec -i linux-container cat /etc/os-release
   

7. Run a command in the Windows container (these will return output).

   docker -c default exec windows-container ping
   docker -c default exec -i windows-container ping
   $null | docker -c default exec windows-container ping
   $null | docker -c default exec -i windows-container ping
   

Expected behavior

The commands in step 5 which run in the Linux container should all return output, but they do not. Only the command in step 6 works, but it relies on having an active stdin (not the case in CI like Azure DevOps pipelines, replicated by the $null | ... commands).

docker version

$ docker -c wsl version
Client:
 Version:           28.3.2
 API version:       1.51
 Go version:        go1.24.5
 Git commit:        578ccf6
 Built:             Wed Jul  9 16:12:31 2025
 OS/Arch:           windows/amd64
 Context:           wsl

Server: Docker Engine - Community
 Engine:
  Version:          28.3.2
  API version:      1.51 (minimum version 1.24)
  Go version:       go1.24.5
  Git commit:       e77ff99
  Built:            Wed Jul  9 16:13:45 2025
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.7.27
  GitCommit:        05044ec0a9a75232cad458027ca83437aae3f4da
 runc:
  Version:          1.2.5
  GitCommit:        v1.2.5-0-g59923ef
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

$ docker -c default version
Client:
 Version:           28.3.2
 API version:       1.51
 Go version:        go1.24.5
 Git commit:        578ccf6
 Built:             Wed Jul  9 16:12:31 2025
 OS/Arch:           windows/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          28.3.2
  API version:      1.51 (minimum version 1.24)
  Go version:       go1.24.5
  Git commit:       e77ff99
  Built:            Wed Jul  9 15:41:13 2025
  OS/Arch:          windows/amd64
  Experimental:     false

docker info

$ docker -c wsl info
Client:
 Version:    28.3.2
 Context:    wsl
 Debug Mode: false

Server:
 Containers: 2
  Running: 2
  Paused: 0
  Stopped: 0
 Images: 5
 Server Version: 28.3.2
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 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: 05044ec0a9a75232cad458027ca83437aae3f4da
 runc version: v1.2.5-0-g59923ef
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.6.87.2-microsoft-standard-WSL2
 Operating System: Ubuntu 24.04.2 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 16
 Total Memory: 62.8GiB
 Name: mark-test-vm2
 ID: c8957280-19af-4e36-86d7-fac6425f4b5b
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false

[DEPRECATION NOTICE]: API is accessible on http://0.0.0.0:2375 without encryption.
         Access to the remote API is equivalent to root access on the host. Refer
         to the 'Docker daemon attack surface' section in the documentation for
         more information: https://docs.docker.com/go/attack-surface/
In future versions this will be a hard failure preventing the daemon from starting! Learn more at: https://docs.docker.com/go/api-security/

$ docker -c default info
Client:
 Version:    28.3.2
 Context:    default
 Debug Mode: false

Server:
 Containers: 1
  Running: 1
  Paused: 0
  Stopped: 0
 Images: 3
 Server Version: 28.3.2
 Storage Driver: windowsfilter
  Windows:
 Logging Driver: json-file
 Plugins:
  Volume: local
  Network: ics internal l2bridge l2tunnel nat null overlay private transparent
  Log: awslogs etwlogs fluentd gcplogs gelf json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Swarm: inactive
 Default Isolation: process
 Kernel Version: 10.0 20348 (20348.1.amd64fre.fe_release.210507-1500)
 Operating System: Microsoft Windows Server Version 21H2 (OS Build 20348.3932)
 OSType: windows
 Architecture: x86_64
 CPUs: 16
 Total Memory: 128GiB
 Name: mark-test-vm2
 ID: 27828f3f-c78c-4bc9-b7f3-f2fbeee7f3ae
 Docker Root Dir: C:\ProgramData\docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine

Additional Info

Docker client is on Windows, Docker daemon is on WSL 2 (Ubuntu). Tested via Windows Sever 2022 running in Azure.

If you add the debug flag -D to the commands you can see some extra output which could help with troubleshooting:

$null | docker -D -c default exec -i windows-container ping
(...output...)
time="2025-07-29T18:40:58Z" level=debug msg="[hijack] End of stdin"
time="2025-07-29T18:40:58Z" level=debug msg="[hijack] End of stdout"

docker -D -c wsl exec -i linux-container cat /etc/os-release
(...output...)
time="2025-07-29T18:43:24Z" level=debug msg="[hijack] End of stdout"

$null | docker -D -c wsl exec -i linux-container cat /etc/os-release
time="2025-07-29T18:42:17Z" level=debug msg="[hijack] End of stdin"
time="2025-07-29T18:42:17Z" level=debug msg="[hijack] End of stdout"

Start by reproducing the listed docker exec commands on the Windows client with a WSL daemon, comparing active and absent stdin, and review the related Docker CLI issues and PRs. Trace the exec output and stdin handling from the CLI entry point; done means Linux-container commands consistently print output in interactive and CI-like environments without regressing Windows-container behavior.