Is Docker running within WSL or connecting back to Windows?

Question

After successfully installing Docker in WSL, if I run standard Docker commands, I get connection errors. Runing with sudo or not yields the same result in all examples.

root@SUR002731165154:~# sudo docker info
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

root@SUR002731165154:~# sudo docker version
Client:
Version:      1.13.1
API version:  1.26
Go version:   go1.7.5
Git commit:   092cba3
Built:        Wed Feb  8 06:42:29 2017
OS/Arch:      linux/amd64
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

However, if I add -H localhost:2375 to the command I can run Docker no problem. Is Docker connecting to my localhost Windows 10 machine or is it running locally on WSL, or is doing a bit of both?

root@SUR002731165154:~# docker -H localhost:2375 version
Client:
Version:      1.13.1
API version:  1.26
Go version:   go1.7.5
Git commit:   092cba3
Built:        Wed Feb  8 06:42:29 2017
OS/Arch:      linux/amd64

Server:
Version:      1.13.1
API version:  1.26 (minimum version 1.12)
Go version:   go1.7.5
Git commit:   092cba3
Built:        Wed Feb  8 08:47:51 2017
OS/Arch:      linux/amd64
Experimental: true

root@SUR002731165154:~# docker -H localhost:2375 info
Containers: 11
Running: 0
Paused: 0
Stopped: 11
Images: 8
Server Version: 1.13.1
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: aa8187dbd3b7ad67d8e5e3a15115d3eef43a7ed1
runc version: 9df8b306d01f59d3a8029be411de015b7304dd8f
init version: 949e6fa
Security Options:
seccomp
Profile: default
Kernel Version: 4.9.8-moby
Operating System: Alpine Linux v3.5
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 1.934 GiB
Name: moby
ID: 4LYM:R5T5:6CPZ:Z2KC:YQ4R:NGN4:V6SR:DF7E:YPYO:7FHY:EQW5:2T7W
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): true
File Descriptors: 13
Goroutines: 21
System Time: 2017-02-28T18:54:13.7726687Z
EventsListeners: 0
Registry: https://index.docker.io/v1/
Experimental: true
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false

Answer 1

The Docker daemon can't run under WSL as it doesn't implement the necessary kernel ABI's. If you're running Docker for Windows, you are probably connecting to the Hyper-V virtual machine that it manages.

Because it's on a different machine, you will not be able to mount WSL directories as Docker volumes, but you can build images from a WSL directory. This is because on a build, the client creates a tarball and sends it to the daemon.

Answer 2

This is a workaround which is to use Docker on windows in WSL instead.

Just add the following to your WSL .bashrc file.

export PATH="$HOME/bin:$HOME/.local/bin:$PATH"
export PATH="$PATH:/mnt/c/Program\ Files/Docker/Docker/resources/bin"
alias docker=docker.exe
alias docker-compose=docker-compose.exe

Reference: https://blog.jayway.com/2017/04/19/running-docker-on-bash-on-windows/