n/nextcloud.md: look at, contemplate and link official documentation

n/nextcloud.md

@@ -22,16 +22,45 @@ sudo flatpak override com.nextcloud.desktopclient.nextcloud --filesystem=~/Nextc
 
 ## Sysadmin
 
-**_Go away._** This is likely highly specific to an undisclosed location.
+**_Go away._** This is likely highly specific to an undisclosed theoretical
+location. Maybe look into
+[official documentation](https://docs.nextcloud.com/server/stable/admin_manual/occ_command.html)
+instead?
+
+There is an environment variable `NC_debug` for which NextCloud keeps telling
+you to `sudo --preserve-env` aka `-E`. I disagree, `sudo` is fully capable of
+`Defaults        env_keep += "NC_debug"` with potentially less unforeseen
+consequences.
 
 ```bash
+# Everything is expected to be ran in the NextCloud / ownCloud Console
+# directory, which in this case means
 cd /var/www/html
-# Untested
+
+# Usage instructions
 sudo -u www-data php --define apc.enable_cli=1 occ --help
+
+# Status. Has flags --output=json[,pretty}
+sudo -u www-data php --define apc.enable_cli=1 occ status
+
 # Example: self-repair?
 sudo -u www-data php --define apc.enable_cli=1 occ maintenance:repair
+
 # Disable maintenance-mode
 sudo -u www-data php --define apc.enable_cli=1 occ maintenance:mode --off
-# Self-upgrade?
+
+# Post-upgrade routine tasks once new version is downloaded.
 sudo -u www-data php --define apc.enable_cli=1 occ upgrade
+
+# Display apps pending update. Remove flag for actually updating.
+sudo -u www-data php --define apc.enable_cli=1 occ app:update --showonly
 ```
+
+### Interesting keywords for perusing official documentation
+
+- `sudo -u www-data php --define apc.enable_cli=1 occ files:transfer-ownership`
+- `sudo -u www-data php --define apc.enable_cli=1 occ maintenance`
+- `sudo -u www-data php --define apc.enable_cli=1 occ security`
+- `sudo -u www-data php --define apc.enable_cli=1 occ user`
+  - `sudo -u www-data php --define apc.enable_cli=1 occ user:report`
+- `sudo -u www-data php --define apc.enable_cli=1 occ setupchecks`