So I have a use case where I need to detect inside of a WSL2 VM whether the Docker setup is Docker for Windows w/ WSL integration vs Docker just running inside of the WSL VM (say installed directly via apt or dnf). The networking situation between these two use cases is different because with Docker for Windows WSL integration you cannot reach containers by their IP from the WSL VM. This poses some problems for some dev-tooling that we have and wasn't previously an issue with devs running on Linux-native machines but we've recently run into it now that some devs are using Windows machines with WSL and Docker for Windows.
Any thoughts on how I can do this? Look for specific env vars, mount points etc?
Looks like I can just stat /mnt/wsl/docker-desktop and see if that exists.
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From what I understand, the container includes all dependencies to run, but all containers running on the same platform whether it's a VM, or bare-metal will share the underlying kernel.
I believe I read somewhere that in order to run linux containers on windows, the Docker client spins up a linux based VM, and runs the container in that.
But now I see that docker for windows runs linux containers natively (ie, without hyper-v).
My question is: How can an image that was built to run on linux run on a system that has a windows kernel?
This is the original source that my question arose from:
https://www.hanselman.com/blog/DockerAndLinuxContainersOnWindowsWithOrWithoutHyperVVirtualMachines.aspx
With the latest version of Windows 10 (or 10 Server) and the beta of
Docker for Windows, there's native Linux Container support on Windows.
That means there's no Virtual Machine or Hyper-V involved (unless you
want), so Linux Containers run on Windows itself using Windows 10's
built in container support.
I saw some similar questions, but they explained how a linux container runs on a windows platform by utilising a vm/hyper-v
How docker desktop runs linux containers on Windows machine
Does "Docker On Windows" launch a linux virtual machine?
Perhaps I didn't understand their answers, but from what I understood, it still seems like the linux container is sitting on-top of the windows kernel.
this is the magic of LCOW (https://github.com/linuxkit/lcow)
you are right to run a container the base KERNEL should be same , since container is just an abstraction , so to run a linux container on windows there are two options
either use moby linux on hyperv and run containers there
use lcow to run light weight linux vm for each container. (lcow)
https://learn.microsoft.com/en-us/virtualization/windowscontainers/deploy-containers/linux-containers
with WSL in windows in future we might be able to get a third method don't know if already someone is working on it .
here's the thing: I tried to install docker inside a windows which runs inside virtualbox, and off course I failed due it's not possible (now I know this is due Hyper-V not used by virtualbox and required by docker).
Since for me migrating to VMWare ain't an option, I dig a little bit and found out that there's no problem on running docker inside a linux distro (which runs inside a vbox), so here's the question.
Is it possible to run 2 different virtual machines with virtualbox, one with linux (running docker inside it), and the other one with windows as my development environment, both at the same time and to develop on windows and then deploy and run tests on docker? If this is possible, how? Any links or keywords for me to search for would be appreciated.
Sure! You need to do following steps:
You should set your VMs network so then can see easily each other https://superuser.com/questions/119732/how-to-do-networking-between-virtual-machines-in-virtualbox
You should expose docker daemon on TCP socket on VM with linux https://success.docker.com/article/how-do-i-enable-the-remote-api-for-dockerd
On VM with windows you need to create some override for docker client so he will connect to remote daemon on linux machine https://gist.github.com/kekru/4e6d49b4290a4eebc7b597c07eaf61f2#create-bat-file-for-windows
Please keep in mind when you expose some service under ports you won't access that on VM with windows on localhost - instead of that you need to type: :
When using Docker for Windows, you must choose to either use Windows or Linux containers, but you can't use both at the same time. What is the technical reason(s) for this? It's a little counter-intuitive, since each container has its own isolated operating system.
Linux containers on Docker for Windows are not handled by windows itself, but they are using Hyper-V Linux VM - MobyLinuxVM. Hence the necessity to switch between Linux and Windows.
However starting from Windows 1709 and Docker in edge version you can try out linux containers on windows - see: https://blog.docker.com/2017/09/docker-windows-server-1709/
Update
As #v.karbovnichy brought up, technically on Docker for Windows you "can" run linux and windows containers simultanously - you can use docker-machine command to create additional linux-based virtual machine that will run your linux containers. Then, you can connect them into one swarm and, with a dose of good will, you will run linux and windows containers simultaneously on same machine.
docker client command itself can connect to both linux or windows docker-server and "manage" both of them - check docker login - it's widely used in server configurations.
However as stated above, true running linux and windows containers next to each other is in preview state.
Docker ecosystem on your Windows machine contains several components.
One is Docker command line: the docker command that you use for everything-management. The second one is Docker daemon - A self-sufficient runtime for containers, the core.
Docker daemons for Linux Containers and Windows Containers are different, but they listen for connections from the docker client on the same pipe. So one needs to be stopped for other to be started. This is the technical reason that you asked for.
However, you can observe that containers started for ex. in MobyLinuxVM is still running and available for connections when you switch to Windows containers. The only thing here is that you cannot manage them because the Docker daemon for Windows does not know how to manage Linux containers in MobyLinuxVM.
UPDATE: As described in this post,
Docker for Windows 18.02 now supports Linux and Windows containers running side-by-side via LCOW, using a single Docker daemon.
So actually now you can use one docker daemon to manage both worlds, it's just about using the new --platform flag in docker pull.
I am using Win 10 Pro N (Version 1709) as a development machine and Windows Server 2016 Standard (Version 1607) as production server.
I am currently developing an ASP.NET Core 2 application with MongoDb as database.
A couple days ago I first stumbled over the idea, to run MongoDb as a Docker image.
I don't have any experience with Docker so far, but I managed to switch from Linux containers (default) to Windows containers on Windows machines.
Was this a good decision? Or is there any reason why I should use Linux containers instead of Windows containers in my scenario?
What e.g. if I should decide to deploy my application to a Linux server some time? In this case, would it wiser to start with Linux containers right from the beginning?
Docker is not about virtualization but more about isolation.
A windows container will run on a windows host
A linux container will run on a linux host
Then some people wanted to run linux container on windows
First you needed to create a linux vm on windows to run the container
Now you can use LinuxKit to run the container but it's still a light VM
Then some people wanted to run windows container on linux
First you needed to create a windows vm on linux to run the container
Now you can use nothing more as of today
So the best bet is to start with a container aimed at your production servers
If you want to deploy to linux I would advise using linux containers since you then test a more similar setup and are more likely to find issues that will also show in your final deployment.
Other than that linux container technology is more mature and better supported than windows containers.
I have a following scenario:
Windows 7 machine, with an ubuntu virtual machine through virtual box.
I want to know what are the best options for running docker inside the ubuntu?
Can I just install the docker to the ubuntu? Or should I use docker-machine?
The official specs left me confused by saying:
Machine is currently the only way to run Docker on Mac or Windows
So according to that, it would mean I do need the docker-machine, since my base system is Windows?
Why couldn't I just install docker to the virtual machine ubuntu, and use it directly there?
I believe you can but haven't tried this myself. The comment about Docker Machine is related to not being able to run Docker directly on the Windows OS. Docker Machine is spinning up a headless Virtualbox instance of boot2docker with a convenient cli to access it.