nixos/doc: mention "No such file or directory" error on Nextcloud

That was... interesting to debug. It took a me a bit of reading C code
until I realized that the realpath cache is internally used for
`file_get_contents`, but not for `file_exists` 🙃

I'm not comfortable on doing the workaround in the module, but I think
it's good to have this documented in the manual.
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Maximilian Bosch 2024-09-16 18:57:10 +02:00
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@ -144,6 +144,42 @@ Auto updates for Nextcloud apps can be enabled using
To work around that, please make sure that all directories in question
are owned by `nextcloud:nextcloud`.
- **`Failed to open stream: No such file or directory` after deploys**
Symptoms are errors like this after a deployment that disappear after
a few minutes:
```
Warning: file_get_contents(/run/secrets/nextcloud_db_password): Failed to open stream: No such file or directory in /nix/store/lqw657xbh6h67ccv9cgv104qhcs1i2vw-nextcloud-config.php on line 11
Warning: http_response_code(): Cannot set response code - headers already sent (output started at /nix/store/lqw657xbh6h67ccv9cgv104qhcs1i2vw-nextcloud-config.php:11) in /nix/store/ikxpaq7kjdhpr4w7cgl1n28kc2gvlhg6-nextcloud-29.0.7/lib/base.php on line 639
Cannot decode /run/secrets/nextcloud_secrets, because: Syntax error
```
This can happen if [](#opt-services.nextcloud.secretFile) or
[](#opt-services.nextcloud.config.dbpassFile) are managed by
[sops-nix](https://github.com/Mic92/sops-nix/).
Here, `/run/secrets/nextcloud_secrets` is a symlink to
`/run/secrets.d/N/nextcloud_secrets`. The `N` will be incremented
when the sops-nix activation script runs, i.e.
`/run/secrets.d/N` doesn't exist anymore after a deploy,
only `/run/secrets.d/N+1`.
PHP maintains a [cache for `realpath`](https://www.php.net/manual/en/ini.core.php#ini.realpath-cache-size)
that still resolves to the old path which is causing
the `No such file or directory` error. Interestingly,
the cache isn't used for `file_exists` which is why this warning
comes instead of the error from `nix_read_secret` in
`override.config.php`.
One option to work around this is to turn off the cache by setting
the cache size to zero:
```nix
services.nextcloud.phpOptions."realpath_cache_size" = "0";
```
## Using an alternative webserver as reverse-proxy (e.g. `httpd`) {#module-services-nextcloud-httpd}
By default, `nginx` is used as reverse-proxy for `nextcloud`.