FPM: 404 / File not found

[jatofg]

I'm trying to get the fpm docker image running, but encounter the issue that php-fpm will just give me a 404 "File not found." response for every request.

My docker-compose looks like this:

services:
  roundcubemail:
    image: roundcube/roundcubemail:latest-fpm
    container_name: roundcubemail
    restart: unless-stopped
    volumes:
      - /opt/roundcube/www_html:/var/www/html
      - /opt/roundcube/config:/var/roundcube/config
      - /opt/roundcube/enigma:/var/roundcube/enigma
      - /opt/roundcube/db:/var/roundcube/db
    environment:
      - ROUNDCUBEMAIL_DB_TYPE=sqlite
      - ROUNDCUBEMAIL_SKIN=elastic
      - ROUNDCUBEMAIL_DEFAULT_HOST=tls://[...]
      - ROUNDCUBEMAIL_SMTP_SERVER=tls://[...]
      - ROUNDCUBEMAIL_PLUGINS=archive,zipdownload,password
      - ROUNDCUBEMAIL_UPLOAD_MAX_FILESIZE=20M
    ports:
      - "127.0.0.1:9001:9000"

After starting the container, the Roundcube files are successfully copied to /opt/roundcube/www_html and an SQLite database is created inside /opt/roundcube/db.

Apache configuration:

<Directory "/opt/roundcube/www_html/public_html/">
<FilesMatch \.(php)$>
  <If "-f %{SCRIPT_FILENAME}">
    SetHandler proxy:fcgi://localhost:9001
  </If>
</FilesMatch>
Require all granted
AllowOverride all
</Directory>

Requests to the roundcube domain are then successfully served by PHP-FPM inside of the container, but every request gives me an HTTP 404 with the content "File not found. " I assume this comes from the FPM service, but it is as well possible that it comes from Roundcube. However, I'm unable to find any helpful logs anywhere.

I've also tried to use SetHandler proxy:fcgi://localhost:9001/var/www/html/ in case the image serves / instead of the Roundcube files, which was my first assumption, but with the same result.

docker logs roundcubemail gives me the following log:

Running pre-setup tasks:
roundcubemail found in /var/www/html - installing update...
Target installation already in version 1.6.13. Do you want to update again? (y/N)
Copying files to target location...done.

Running update script at target...
Executing database schema update.
This instance of Roundcube is up-to-date.
Have fun!
All done.
Composer could not detect the root package (roundcube/roundcubemail) version, defaulting to '1.0.0'. See https://getcomposer.org/root-version
Installing dependencies from lock file
Verifying lock file contents can be installed on current platform.
Warning: The lock file is not up to date with the latest changes in composer.json. You may be getting outdated dependencies. It is recommended that you run `composer update` or `composer update <package name>`.
Nothing to install, update or remove
Package pear/console_commandline is abandoned, you should avoid using it. No replacement was suggested.
Generating optimized autoload files
4 packages you are using are looking for funding.
Use the `composer fund` command to find out more!
Write Docker config to /var/www/html/config/config.docker.inc.php
Checking for database schema updates...
Running post-setup tasks:
[17-Feb-2026 18:57:18] NOTICE: fpm is running, pid 1
[17-Feb-2026 18:57:18] NOTICE: ready to handle connections
172.18.0.1 -  17/Feb/2026:19:05:04 +0000 "HEAD /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:04 +0000 "HEAD /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:05 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:05 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:32 +0000 "HEAD /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:32 +0000 "HEAD /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:32 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:33 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:38 +0000 "HEAD /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:38 +0000 "HEAD /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:38 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:19:05:38 +0000 "GET /index.php" 404
[...]
172.18.0.1 -  17/Feb/2026:20:30:42 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:43 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:44 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:44 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:44 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:44 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:44 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:44 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:45 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:45 +0000 "GET /index.php" 404
172.18.0.1 -  17/Feb/2026:20:30:45 +0000 "GET /index.php" 404

Either something is wrong with the image, or I missed something out (in the latter case I wish the documentation was better).

[pabzm]

This is not really a bug report or feature request, but rather a request for debugging help, thus I'm converting it to a discussion.

Please use issues only for concrete bug reports or feature requests.

[pabzm]

I'm not an apache expert, but I think you should try to use SetHandler proxy:fcgi://localhost:9001/var/www/html/public_html, since that's the correct path to the docroot inside the FPM container.

[jatofg]

I've finally managed to get it running using

ProxyPassMatch "^/.*\.php(/.*)?$" "fcgi://localhost:9001/var/www/html/" enablereuse=on

Documentation on how to use the fpm inside of the container, ideally with some examples, would be helpful. I couldn't find any apart from a docker-compose file.