I’m a retired Unix admin. It was my job from the early '90s until the mid '10s. I’ve kept somewhat current ever since by running various machines at home. So far I’ve managed to avoid using Docker at home even though I have a decent understanding of how it works - I stopped being a sysadmin in the mid '10s, I still worked for a technology company and did plenty of “interesting” reading and training.
It seems that more and more stuff that I want to run at home is being delivered as Docker-first and I have to really go out of my way to find a non-Docker install.
I’m thinking it’s no longer a fad and I should invest some time getting comfortable with it?
I would absolutely look into it. Many years ago when Docker emerged, I did not understand it and called it “Hipster shit”. But also a lot of people around me who used Docker at that time did not understand it either. Some lost data, some had servicec that stopped working and they had no idea how to fix it.
Years passed and Containers stayed, so I started to have a closer look at it, tried to understand it. Understand what you can do with it and what you can not. As others here said, I also had to learn how to troubleshoot, because stuff now runs inside a container and you don´t just copy a new binary or library into a container to try to fix something.
Today, my homelab runs 50 Containers and I am not looking back. When I rebuild my Homelab this year, I went full Docker. The most important reason for me was: Every application I run dockerized is predictable and isolated from the others (from the binary side, network side is another story). The issues I had earlier with my Homelab when running everything directly in the Box in Linux is having problems when let´s say one application needs PHP 8.x and another, older one still only runs with PHP 7.x. Or multiple applications have a dependency of a specific library when after updating it, one app works, the other doesn´t anymore because it would need an update too. Running an apt upgrade was always a very exciting moment… and not in a good way. With Docker I do not have these problems. I can update each container on its own. If something breaks in one Container, it does not affect the others.
Another big plus is the Backups you can do. I back up every docker-compose + data for each container with Kopia. Since barely anything is installed in Linux directly, I can spin up a VM, restore my Backups withi Kopia and start all containers again to test my Backup strategy. Stuff just works. No fiddling with the Linux system itself adjusting tons of Config files, installing hundreds of packages to get all my services up and running again when I have a hardware failure.
I really started to love Docker, especially in my Homelab.
Oh, and you would think you have a big resource usage when everything is containerized? My 50 Containers right now consume less than 6 GB of RAM and I run stuff like Jellyfin, Pi-Hole, Homeassistant, Mosquitto, multiple Kopia instances, multiple Traefik Instances with Crowdsec, Logitech Mediaserver, Tandoor, Zabbix and a lot of other things.
The backup and easy set up on other servers is not necessarily super useful for a homelab but a huge selling point for the enterprise level. You can make a VM template of your host with docker set up in it, with your Compose definitions but no actual data. Then spin up as many of those as you want and they’ll just download what they need to run the images. Copying VMs with all the images in them takes much longer.
And regarding the memory footprint, you can get that even lower using podman because it’s daemonless. But it is a little more work to set things up to auto start because you have to manually put it into systemd. But still a great option and it also works in Windows and is able to parse Compose configs too. Just running Docker Desktop in windows takes up like 1.5GB of memory for me. But I still prefer it because it has some convenient features.
It seems like docker would be heavy on resources since it installs & runs everything (mysql, nginx, etc.) numerous times (once for each container), instead of once globally. Is that wrong?
You would think so, yes. But to my surprise, my well over 60 Containers so far consume less than 7 GB of RAM, according to htop. Also, of course Containers can network and share services. For external access for example I run only one instance of traefik. Or one COTURN for Nextcloud and Synapse.