Difference between Fly VM and an app deployed with Docker container?

As the title says, what’s the difference? I don’t understand the difference between the two? By VM do you mean Fly VMs are full-fledged KVM machines?

Yes, they are full-fledged KVM machines.

They have their own kernel and share nothing with the host.

We have our own init program (PID 1) to make things easier for Docker images which often don’t include one.

@jerome How do I deploy a VM instead of a Docker app?

All Fly instances are VMs, none of them are docker containers. We just extract the Docker image to the root drive of the VM.

Launching an app or a Fly Machine will get your a VM. The latter is more flexible.

@jerome In that case I launched Ubuntu container and installed openssh-server but in the VM I can’t install LXC for example

Here is my Dockerfile:

FROM ubuntu

RUN apt-get update

RUN apt-get install -y openssh-server
RUN mkdir /var/run/sshd

RUN echo 'root:mypassword' | chpasswd

RUN sed -ri 's/^#?PermitRootLogin\s+.*/PermitRootLogin yes/' /etc/ssh/sshd_config
RUN sed -ri 's/UsePAM yes/#UsePAM yes/g' /etc/ssh/sshd_config

RUN mkdir /root/.ssh

RUN apt-get clean && \
    rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*


CMD ["/usr/sbin/sshd", "-D"]

What commands are your using and what error are you getting when trying to install LXC?

@jerome Is it possible to deploy a bare VM?

@jerome This is the error I’m getting

root@a28992a0:~# snap install lxd
error: cannot communicate with server: Post http://localhost/v2/snaps/lxd: dial unix /run/snapd.socket: connect: no such file or directory

Running a Docker image like you’re doing is pretty much as bare as it gets.

Looks like you need to run the snapd server in the background first.

There’s no systemd running in these VMs. There’s no systemd included in the Ubuntu docker images anyway. It looks like the easiest way to use snaps is to use systemd.

You might be able to make it work by running snapd & and then retrying.

However, it’s likely easier to use aptitude:

apt update
apt install lxc
# ...

Instructions here: Containers - lxc | Ubuntu


Command '/usr/bin/lxd' requires the lxd snap to be installed.
Please install it with:

snap install lxd

Is it not possible to deploy a VM that has systemd included? Or maybe a way just to deploy a bare VM?

All our VMs require a Docker-like image. The “barest” would be using the Docker scratch image, but you wouldn’t be able to do anything with it.

We always include our own init program as PID 1 because 99.9% of Docker images don’t include a useful PID 1 program (reaping zombies and all that).

Our init also does more, like collecting metrics, forwarding logs, etc.

I’m sure you can run systemd as something other than PID 1, but you’ll have to figure that out yourself. We can only help so much.

You can install lxd without snap: apt install lxd.

You’ll have to do more troubleshooting on your own, we can’t hold your hand through every command you run. I know nothing about LXC and only had to do 2 Google searches to figure out how to run it without snap.

I don’t want it either. I never didn’t ask for hand-holding.

I installed lxd with apt. But running “lxd init” errors out that it requires the snap package.

Anyways, thank you for your efforts :smiley: