Managing your gemini feeds with Comitium and docker

Thursday, April 8, 2021



If you read this blog before, you know that I’ve become a big fan of the gemini space and that I do run a capsule with specific content on there :). I’ve been enjoying reading many gemlog over the past months and the list is growing :).

As for the web, following every capsules is hard to do “manually” and as for the web, having a feed reader is very useful :). Until now, I have been using the built-in capability of amfora gemini browser to subscribe to feeds and it has worked flawlessly (I love this browser :)). But the issue I have with it is that it is link to my laptop and the local installation of amfora. If I browse the gemini space on my phone, I still need to see what’s new in the capsule I follow. I won’t write more about this, this is the same idea of having a web rss feed like freshrss or miniflux.

I won’t talk about how much I love following gemlogs at the moment and how it reminds me of the early days of following bloggers online as it will be the goal of a dedicated gemlog post^^.

There are multiple feed readers for gemini, like Gemreader, Gmisub, Moku-Pona, comitium, and probably others…

I selected comitium in the end, as it seemed very simple to install and manage. And it does exactly what I need :]. So far, it has worked for a couple of days quite nicely :).


So first thing first, as you know, I manage everything in docker in my self hosted environment. As always, I’m not saying this is the right way of doing it, just a way I enjoy ^^.

Anyway, no need to deploy a swarm stack for comitium, I just need to run it every X hours to refresh the feeds. I could have installed comitium on one of the node, but I didn’t want to install go locally on the host. So let’s use a very simple image to create the gmi files. Comitium will generate files to deploy to your gemini server. More on that later.

Image Creation

No public image yet to reuse, but as you know I like having my own built images. I have my “preprod” rpi with my local registry on it as explained here.

This is an example of an extremely simple Dockerfile:

FROM golang:1.15

   git clone && cd scdoc && \
   make && make install && cd ..
   git clone && cd comitium && \
   make && make install

VOLUME /data

No entrypoint or command as we will have to use different commands (add/remove/refresh).

Then, build the image:

docker build .

If it works, you can tag the image:

docker build . -t registry.local:5000/b55-comitium:latest

Then, you can do a test run:

docker run -it --rm -v /home/pi/testdir/comitium/data/:/data registry.local:5000/b55-comitium:latest comitium add <GeminiFeedUrl> -d /data

It should generate files in the data directory (feeds.gmi, subscriptions.gmi, comitium.json).

Usage on the cluster

So let’s deploy it on the cluster. Ssh to one of the node and:

docker pull registry.local:5000/b55-comitium:latest

Should pull the image from the registry. Adapt to your url/port.

Create the data where the files needs to be generated. It could be in a directory of your servers or anywhere. In my case, I prefer generating it in a dedicated directory and then rsync it in the right directory for the server.

mkdir /path/to/comitium/data

Then you can add a feed to test. Same command as on freeza:

docker run -it --rm -v /path/to/comitium/data/:/data registry.local:5000/b55-comitium:latest comitium add <GeminiFeedUrl> -d /data

It should generate the files as said above.

Nota: You can customize the header of the page by providing a header.gmi file.

In my case, I simply use a header.gmi file containing (with the empty line at the end):

# Bacardi55's gemini feed subscriptions
=> This page is generated with comitium

To refresh the data, this command could be used:

docker run -it --rm -v /path/to/comitium/data/:/data registry.local:5000/b55-comitium:latest comitium refresh -d /data

Also, because I make comitium create this files not in the server directory, I need to rsync the files to the right directory:

rsync -avzhP /path/to/comitium/data/ /path/to/server/feed/data/

Now, what I’d like is running comitium on its own hostname, not inside my current capsule. In my case, I run it publicly on gemini:// You can have a look at it if you want. So I need to copy the feeds.gmi file as an index.gmi file so it is delivered automatically by the server.

cp /path/to/server/feed/data/feeds.gmi /path/to/server/feed/data/index.gmi

Now that’s cool, but adding and removing feeds with the long docker command, the cp and then running rsync is quite boring…

To simplify this, I created 2 bash functions in my bashrc:

comitium-add() {
  docker run --rm -v /path/to/comitium/data/:/data registry.local:5000/b55-comitium:latest comitium add "$1" -d /data
  rsync -avzhP /path/to/comitium/data/ /path/to/server/feed/data/
  cp /path/to/server/feed/data/feed.gmi /path/to/server/feed/data/index.gmi

comitium-remove() {
  docker run --rm -v /path/to/comitium/data/:/data registry.local:5000/b55-comitium:latest comitium remove "$1" -d /data
  rsync -avzhP /path/to/comitium/data/ /path/to/server/feed/data/
  cp /path/to/server/feed/data/feed.gmi /path/to/server/feed/data/index.gmi

And now, simply running comitium-add <FeedUrl> and comitium-remove <FeedUrl> to manage feeds.

Now, that’s great but what we need to finish the setup is a cronjob to refresh the feeds. The simpler is instead of a bash function create a simple shell script that will do the necessary commands. Create the file with the following content:


docker run --rm -v /path/to/comitium/data/:/data registry.local:5000/b55-comitium:latest comitium refresh -d /data
rsync -avzhP /path/to/comitium/data/ /path/to/server/feed/data/
cp /path/to/server/feed/data/feed.gmi /path/to/server/feed/data/index.gmi

Make it executable:

chmod +x /path/to/

Then crontab -e to add the job:

30 */6 * * * /path/to/ > /tmp/cr.log 2>&1

And that should be it. Yes, I only update it every 6 hours, that is enough for me.

Configure your server to run the files as wished. In my case, I just added a second hostname in gmnisrv:



And that should be it (:.


If you find any issue or have any question about this article, feel free to reach out to me via email, mastodon or even IRC, see the About Me page for details.

See Also

Using multiple traefik middlewares using docker labels

Moving gmnisrv to my swarm cluster