Avoiding Pitfalls with Quotation Marks in Docker Compose Environment Variables

Navigating Docker Compose environment variables: Best practices for seamless configuration.
Navigating Docker Compose environment variables: Best practices for seamless configuration.

When working with Docker Compose, setting environment variables is a common task. However, the way you format these variables can lead to unexpected issues, especially when dealing with quotation marks. In this post, we’ll explore a recent challenge I faced with the uptime monitoring tool Gatus and provide best practices to avoid similar problems.

The Problem

I recently tried to set up Gatus using Docker Compose. My initial docker-compose.yml looked something like this:

    container_name: gatus
    image: twinproduction/gatus:latest
    restart: unless-stopped
      - "88:8080"
      - GATUS_CONFIG_PATH="/config"

However, Gatus failed to locate the configuration files at /config. After some troubleshooting, I found that the issue was with the quotation marks around the environment variable value. Removing the quotation marks resolved the problem:

    container_name: gatus
    image: twinproduction/gatus:latest
    restart: unless-stopped
      - "88:8080"
      - GATUS_CONFIG_PATH=/config

Understanding the Issue

Docker Compose uses YAML for configuration, and YAML handles quotation marks in a specific way. When you enclose a value in quotation marks, those quotes become part of the value. In the case of a minimal Docker image like Gatus, which is built from scratch, the shell interprets these quotes literally, causing it to fail to find the intended path:

  • With quotes:
    sets the variable to the literal string "/config", including the quotes.
  • Without quotes:
    sets the variable to the string /config, as intended.

Docker Compose Environment Variables

Array Format vs. Key-Value Pairs Format

Docker Compose allows environment variables to be defined in two ways:

Array Format
     - MY_VAR=value
     - MY_OTHER_VAR="another value"
Key-Value Pairs Format
     MY_VAR: value
     MY_OTHER_VAR: "another value"

When to Use Quotation Marks

  • Without Quotation Marks:
    For simple strings without spaces, special characters, or reserved YAML characters, omit the quotes:
    MY_VAR: value
  • With Quotation Marks:
    Use quotes for values with spaces or special characters to ensure proper parsing:
    MY_OTHER_VAR: "another value"


Prefer Key-Value Pairs Format

The key-value pairs format is more readable and avoids some of the parsing issues associated with the array format.

         MY_VAR: value
         MY_OTHER_VAR: "another value"
Use Quotes Judiciously

Only use quotes when necessary to ensure correct parsing and avoid including them in the actual value.

   MY_VAR: simple_value
   MY_OTHER_VAR: "value with spaces"


Quotation marks can lead to subtle issues when setting environment variables in Docker Compose, especially with minimal Docker images like Gatus. By understanding how YAML handles these values and following best practices, you can avoid these pitfalls and ensure your services run smoothly.

vdirsyncer auth failures with baikal

I am using Baïkal as Cal- and CardDAV server.

Today I tried to sync the calendars using vdirsyncer, but it failed to connect to my baikal server always giving me auth errors like that:

$ vdirsyncer discover
Discovering collections for pair my_calendars
warning: Failed to discover collections for martin_cal_remote, use `-vdebug` to see the full traceback.
error: Unknown error occurred: 401, message='Unauthorized', url=URL('https://example.de/dav.php')
error: Use `-vdebug` to see the full traceback.
Baikal system settings page
Baikal system settings page

Also from the -vdebug messages I could not make sense of it, but eventually NICO’S BLOG pointed into the correct direction: vdirsyncer is simply no able to do the digest auth… (and probably will never implement the deprecated standard)

So the solution is to change that to basic auth in baikal’s settings.

Thanks Nico, whoever you are :)

GChat login-cookie generator for mautrix' puppeting bridge

At work we’re using Google Workspace to manage ourself. However, I do have a couple of reservations against those kinds of software. Especially on my google-free mobile I am not able to use it - and thus could not chat with the team on-the-go without Matrix and mautrix’ Google Chat puppeting bridge 🤩

The Problem

It seems Google recently altered authentication, which caused the bridge to adapt and consequently I need to frequently re-authenticate the bridge. In addition, the process of authentication became significantly more complicated: You’d need to login to you google account with some browser, then open the browser’s dev tools to access the cookie data and extract a couple of special cookies in the correct Google domain to create a custom JSON object for the bridge, see the full authentication instructions. However, that causes far too much load in my brain, urging automation!

The Solution

Screenshot of the web extension's popup with some mock data
Screenshot of the web extension's popup with some mock data

The solution should be able to read Google’s cookies and should technically be realisable in just a couple of hours… Thus, a little web seemed to be the most obvious solution: it runs in the browser and it’s pretty simple to read the cookies of some domain.

Thus, I developed a little web extension that is already available for both Firefox and Chromium based browsers. The code is available at the Matrix-GChat Bridge Login Cookie Generator repository on GitHub and pretty simple. The web extension basically consists of only the popup part with an icon sitting in the browsers toolbar. Just imagine the popup as a very simple HTML web page with a little touch of JavaScript sugar. It basically asks the browser for all the cookies for the URL https://chat.google.com

function getAllCookies() {
    if (typeof browser === "undefined") {console.log('trying chrome...')
        return chrome.cookies.getAll({url: "https://chat.google.com"})
    } else {
        return browser.cookies.getAll({url: "https://chat.google.com"});

Those cookies are then iterated to collect the relevant ones for the login-cookie command in a LoginCookie data structure. If it managed to find all the necessary cookies, the corresponding login-cookie string can be generated:

    getCookie() {
        return `login-cookie {
    "compass": "${this.compass}",
    "ssid": "${this.ssid}",
    "sid": "${this.sid}",
    "osid": "${this.osid}",
    "hsid": "${this.hsid}"

and it will be revealed in a text area that get dynamically injected into the popup’s page, together with a little button that will copy the contents of the textarea once clicked:

    button.onclick = function () {
            () => {
                console.log('clipboard successfully set');
            () => {
                console.error('clipboard write failed');
        return false;

Thus, you only need to click the icon in some browser where you’re authenticated to the Google chat and the popup will give you the necessary login-cookie \o/

The Publication

Icon of the web extension, created using dall-e on Hugging Face
Icon of the web extension, created using dall-e on Hugging Face

Building the web extension is a breeze: just zip a couple of files :)
I’ve even automated the process with a nifty script. The real journey was the publication process with Mozilla’s AddOn Directory and the Chrome WebStore. Initially, I developed the extension on my Debian-based Firefox, which only supported web extensions in version 2. But there’s a twist - Chromium dropped full support for version 2… Thus, you will find two manifests in the repository…

The next challenge was the publication itself. It’s all nice and complicated, especially in the chrome web store maze. I submitted the first round of the extension and for review at both platforms. You know it from emails: once sent you see the parts that could need a bit of polishing. So I improved the extension, build pipelines etc and wanted to resubmit a new version. AMO played nice, allowing re-submissions, but Chrome WebStore only allows one submission at a time - frustrated I needed to wait for the review results before creating a new version. The next day, AMO listed the most recent version of the extension it took another day for the Chrome review. In total it took 5 days to get it published at the Chrome WebStore. Not sure why the reviews take so long over there…? Perhaps extra scrutiny? Would actually doubt that, though…


A logo of MEUN: an owl sitting on a street with the MEUN map in the background.
MEUN: treasures in your neighbourhood

Last year, I participated in the Advent of Code challenge and used that opportunity to dig a bit into the Rust universe. That was quite a morish adventure, and to continue on that journey I was looking for small but practically “problems” that can be solved using rust. Under the supervision of an artificial and a natural intelligence, it all started with text recognition in images, followed by a lot of parallel computing (which is really nice in rust!), crawlers, web services, a bit of web assembly, etc…

And accidentally, half a year later a usable tool emerged:

MEUN: Rostock’s largest furniture exchange and upcycling network.

On an interactive map at meun.codeahoi.de users can find all kinds of gems in urban regions, such as Sperrmüll (eg. old furniture or e-waste) and places to share books and clothes. Currently, MEUN focuses on the Rostock region, but there is no technical limitation – it’s simply the region I’m most familiar with ;-)

Technical highlights

MEUN stores it’s data in a PostgreSQL, extended with PostGIS for support with geographic data. The backend service is written in Rust using the Axum framework. Users can register with an email address - there are no passwords in the classical sense. If you register or if you want to login MEUN will send a random one-time password per email, which is valid for an hour. Sessions are realised using axum_sessions. However, the whole “platform” is designed to not require any logins. You can just open MEUN and start browsing through points of interest and create new ones if you discover gems in your urban digressions.

The background vector tiles come from Maptiler. I also use other Maptiler features, such as the coordinate-to-address lookup. MEUN’s PostGIS map data is served by Tegola. The frontend is developed in Angular. The map is integrated using ngx-maplibre-gl and the client state is managed with Elf.

Finally, I need to emphasise that I did not realise all that alone. I never did something useful with Rust before and I haven’t had much experience with geographic information systems (GIS), so I’m really that I received a lot of help by ChatGPT! Not only with the programming, but also with wording and brainstorming and even the acronym. Without ChatGPT, I would never have thought of building “Rostock’s largest furniture exchange and upcycling network!” ;-)
In addition, I received similarly important supervision by my non-AI friend and Rust expert Martin!

I learnt a lot and had tons of fun with my friends. And maybe you find that tool useful as well?

If you have cool ideas on how to improve/extend it or if you find other use cases for such a GIS platform, please let me know. Here as a comment, via email, or through the comment feature on MEUN.

Orbot 17 messes with VPN settings

Orbot Logo from Wikimedia Common
Orbot Logo from Wikimedia Common

I am using Orbot on my linageos mobile phone to route the traffic of certain apps through the TOR network. Since the app updated to some 17.*-BETA-... it changed it’s icon but it apparently also seems to always start in VPN mode. I tried a couple of different settings, but even switching into Power User Mode (!?) didn’t help…

As it’s only possible to run a single VPN on Android, it hijacks the VPN connection of NetGuard: my defense against traffic that is utterly unsolicited. NetGuard blocks connections by providing a VPN, which filters traffic based on the source application the the destination’s server.

Anyway, if Orbot hijacks the VPN slot NetGuard can’t block unwanted traffic anymore.

The workaround is, however, pretty easy. Just open Settings -> Network and Internet -> VPN. Then select your preferred VPN app, that you want to use instead of Orbot. In my case that would be NetGuard. And from that app’s settings enable the Always-on VPN slider. That will prevent Orbot from taking over the next time it connects to the TOR network.

Martin Scharm

stuff. just for the records.

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