👨‍💻 Wesley Moore

Alpine Linux and Docker Infrastructure Three Years Later

Three years ago I published, Rebuilding My Personal Infrastructure With Alpine Linux and Docker, in which I described how I was hosting various applications using an Alpine Linux host and Docker on a virtual machine at Vultr. I thought it would be good to write a follow-up on how this worked out.

The server I set up in 2019 is still running, although it has been through a few Alpine upgrades in that time. Since there are very few packages installed on the host, upgrades are painless. When I originally configured the server Docker Compose was not in the stable Alpine package repos. It was added in the mid-2019 Alpine 3.10 release. I was glad to be able to remove pip and not have to manually manage compose updates after migrating to the package from that point on.

In 2019 the services I was hosting looked like this:

Before

In 2022 the situation is now:

After

As you can see the server is now running more containers. It now hosts a number of new services including a Pleroma instance and several web-applications I built in Rust (leaf, quotes, dewpoint). I also retired the Binary Trance Rails instance and migrated from acme.sh to lego. I ran a Nitter instance for a while but removed it after it bots made it consume a huge amount of bandwidth. See my Burning 2.5Tb of Bandwidth Hosting a Nitter Instance post for more details on that.

The Read Rust application is implemented in Crystal. This one posed a bit of a challenge. It is the only container I run that is not derived from a minimal Alpine base image that I build myself. Instead, it uses debian-slim. I need to use a specific version of the Crystal compiler to build my application, which means I can’t use the version in the Alpine package repos. Additionally the Linux binaries that the project published for this version are not dynamically linked but the bundled libgc.a assumes a glibc based system:

$ crystal build src/asdf.cr
/usr/lib/gcc/x86_64-alpine-linux-musl/10.3.1/../../../../x86_64-alpine-linux-musl/bin/ld: /crystal-0.34.0-1/bin/../lib/crystal/lib/libgc.a(pthread_support.o): in function `GC_thr_init':
pthread_support.c:(.text+0x1137): undefined reference to `gnu_get_libc_version'

For this reason I opted to use a Debian base image for this container and that’s worked fine.

Another notable change is the move from acme.sh to lego for managing TLS certificates. In my original post I noted the following regarding how the certificates were renewed:

Docker and cron is also a challenge. I ended up solving that with a simple solution: use the host cron to docker exec acme.sh in the hitch container. Perhaps not “pure” Docker but a lot simpler than some of the options I saw.

It turned out that this never worked. I could see that cron was running the script but the certs would not get renewed. For a while I ran the script manually to renew them, which did work. Eventually I got sick of this, and thinking acme.sh was to blame I searched for an alternative.

I settled on lego, an ACME client implemented in Go. I discovered and suggested a fix for a bug and contributed LuaDNS support in May 2020 and then migrated over to using it instead of acme.sh. It was in the final stages of test this that I discovered the cron bug was in my script all along. Adding -T to inhibit docker-compose exec from allocating a TTY fixed the issue. It’s likely this would have fixed the issue for acme.sh as well. Ultimately lego felt like the better option as the code in acme.sh for constructing API requests and parsing their results seemed quite fragile

Jokes aside, I still find the Docker workflow of iterating on an image locally then shipping it when it’s working to be quite pleasant. In summary this server has served me well over the last three years and I have no immediate plans to rebuild again. It’s been reliable and mostly hassle free. Hosting on Vultr has also been reliable and stable over that whole time with only the odd interruption for network maintenance or network issues.

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