Selfhosted

A Docker container is essentially a process running on your machine. Just like any other process. It can be idle, stopped or hogging the CPU. You can use Docker constraints to limit resource use if you want to, memory, CPU and network to name a few.

So, can you run 40 processes?

Very likely. Probably 400 or 4000, depending on CPU usage and memory.

I ran that particular CPU with 64 GB of RAM and used it to run multiple virtual machines, my main debian desktop and a VM specifically as a docker host, running dozens of instances of Google Chrome without ever noticing it slowing down.

Then the power cable shortened out and life was never the same. That was six months ago, the machine was a late 2015 iMac running macos and VMware Fusion.

Docker containers arnt virtual machines despite acting like them. They dont actually require compute resources to be sitting around doing nothing like a traditional vm cos they are essentially just a proxy between the kernal in the container and the kernal on the base machine.

If the container isnt doing anything then it isnt consuming resources.

Zero. It seems like software is increasingly expecting to be deployed in a container though, so that probably won't last forever.

None, I use Nix instead. :P

Wandering what the limit is when it comes to how many containers I can run.

Basically the same as the number of processes you can run.

Use "docker stats" to see what resources each container is using.

Run 19 but barely get over 5% usage even when transcoding 4K movies where the copyright has expired.

I am at ~80. Most are idling.

For me, the metric to jeep an eye on is the time spent by the kernel between system and user. If the time spent by in system rises it is the sign that the kernel is just switching of context instead of executing programs.

yes.

You can't really make them go idle, save by restarting them with a do-nothing command like tail -f /dev/null. What you probably want to do is scale a service down to 0. This leaves the declaration that you want to have an image deployed as a container, "but for right now, don't stand any containers up".

If you're running a Kubernetes cluster, then this is pretty straightforward: just edit the deployment config for the service in question to set scale: 0. If you're using Docker Compose, I believe the value to set is called replicas and the default is 1.

As for a limit to the number of running containers, I don't think it exists unless you're running an orchestrator like AWS EKS that sets an artificial limit of... 15 per node? I think? Generally you're limited only by the resources availabale, which means it's a good idea to make sure that you're setting limits on the amount of RAM/CPU a container can use.

I have gone up to about 300-400 or so. Currently running about 5 machines averaging about 100 each.

Looks like 9? Here's what I'm currently running:

• actual budget
• caddy (for TLS trunking)
• nextcloud and collabora
• vaultwarden (currently unused)
• jellyfin
• home assistant

The rest are databases and other auxiliary stuff. I'm probably going to work on it some this holiday break, because I'd like to eventually move to microOS, and I still have a few things running outside of containers that I need to clean up (e.g. Samba).

But yeah, like others said, it really doesn't matter. On Linux (assuming you're not using Docker Desktop), a container is just a process. On other systems (e.g. Windows, macOS, or Linux w/ Desktop), they run in a VM, which is a bit heavier and reserves more resources for itself. I could run 1000 containers and it really wouldn't matter, as long as they're pretty light.

13 containers currently. I have thought about adding some more stuff such as bazarr and more but I need to be in the humor for it.

Right now I have 32 active stacks running and a good number of them create at least one other container like a database. So I’m running around 60+ separate containers. The machine has maybe an i5 6500 or so in it with 32g of ram. I use unraid as the nas platform but I do all the docker stuff manually. It’s plenty fast for what I need so far… :)

On my old Dell workstation I pulled out of the dumpster of a local business, which now has a second life as a Unraid NAS, I’m running 29 currently. Used to be running more, but I got rid of some after I was done using those services.

Among other things, the server runs my entire Servarr stack, as well as the various media servers for video, music, ebooks and audiobooks, and my Gitea. There’s a bunch of other stuff as well, but those are the most important to me.

Big fat zero

Zero.

I run VMs and LDoms at work and VMs at home, a dwindling number of VMware VMs and a growing number of qemus to replace them.

I don't need the hassle.