Is Docker running within WSL or connecting back to

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

As other answers stated, Docker can't be installed and hosted inside WSL but can be used directly from there as any Windows executable.

It may only require an extra effort to make it usable without those pesky .exe extensions: Bash on Windows - alias for exe files. The linked workaround provides a ready to use custom script for easy symlink creation. Symlinks can be freely used inside non-interactive shell scripts unlike bash aliases.

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There is also an approach with connecting from WSL to Docker for Windows as remote host described in https://nickjanetakis.com/blog/setting-up-docker-for-windows-and-wsl-to-work-flawlessly.

If you’re wondering “why not just run docker.exe and docker-compose.exe from Docker for Windows directly in WSL?”, that’s due to a bug with running Docker or Docker Compose interactively in that environment. The TL;DR is you can’t run anything in the foreground with interactive mode, which makes it unusable for real web development.

But sadly there is no reference to exact bug symptoms there. And I didn't face it so far.

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/

Answer 3

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.