# Datenbank sichern:
mariadb-dump -u nc_user -p nextcloud > backup_datei.sql

# Datenbank wiederherstellen:
mariadb -u nc_user -p nextcloud < backup_datei.sql

Wichitge Ordern / Dateien

/etc/apache2/sites-available/nextcloud.conf    - Webserver
/etc/php/8.x/cli/php.ini                       - PHP
/etc/redis/redis.conf                          - Redis
/var/www/nextcloud/.htaccess                   - Nextcloud
/var/www/nextcloud/config/config.php
/var/www/nextcloud/data
/var/www/nextcloud/data/nextcloud.log

cat config.php 
<?php
$CONFIG = array (
  'serverid' => 1,
  'instanceid' => 'oc1fc229f516',
  'htaccess.RewriteBase' => '/',
  'passwordsalt' => 'dpS1ThhU1Y3w54BNw2/jyD2b6XIK8r',
  'secret' => 'rp59N9pW2z5LEqNr4fbE7JH92xvlHa45Rzc+RuPLkQLRVOy1',
  'trusted_domains' => 
  array (
    0 => '10.174.243.51',
  ),
  'datadirectory' => '/var/www/nextcloud/data',
  'dbtype' => 'mysql',
  'version' => '33.0.0.16',
  'overwrite.cli.url' => 'http://10.174.243.51',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'nc_user',
  'dbpassword' => 'nc_pass',
  'installed' => true,
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'redis' => 
  array (
    'host' => 'localhost',
    'port' => 6379,
    'timeout' => 0.0,
  ),
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'default_phone_region' => 'DE',
  'maintenance_window_start' => 1,
  'maintenance' => false,
  'config_preset' => 1,
  'app_install_overwrite' => 
  array (
    0 => 'side_menu',
  ),
);

sudo -u www-data php /var/www/nextcloud/occ

Eine Auswahl von Kommandos

app
  app:disable                            disable an app
  app:enable                             enable an app
  app:getpath                            Get an absolute path to the app directory
  app:install                            install an app
  app:list                               List all available apps
  app:remove                             remove an app
  app:update                             update an app or all apps

 user
  user:add                               adds an account
  user:auth-tokens:add                   [user:add-app-password] Add app password for the named account
  user:auth-tokens:delete                Deletes an authentication token
  user:auth-tokens:list                  List authentication tokens of an user
  user:clear-avatar-cache                clear avatar cache
  user:delete                            deletes the specified user
  user:disable                           disables the specified user
  user:enable                            enables the specified user
  user:info                              show user info
  user:keys:verify                       Verify if the stored public key matches the stored private key
  user:lastseen                          shows when the user was logged in last time
  user:list                              list configured users
  user:profile                           Read and modify user profile properties
  user:report                            shows how many users have access
  user:resetpassword                     Resets the password of the named user
  user:setting                           Read and modify user settings
  user:sync-account-data                 sync user backend data to accounts table for configured users
  user:welcome                           Sends the welcome email
  versions:expire                        Expires the users file versions

files
  files:scan                             rescan filesystem
  files:cleanup                          Clean up orphaned filecache and mount entries
  files:scan-app-data                    rescan the AppData folder
  files:transfer-ownership	         All files and folders are moved to another user - outgoing shares and
                                         incoming user file shares (optionally) are moved as well
maintenance
  maintenance:data-fingerprint           update the systems data-fingerprint after a backup is restored
  maintenance:mimetype:update-db         Update database mimetypes and update filecache
  maintenance:mimetype:update-js         Update mimetypelist.js
  maintenance:mode                       Show or toggle maintenance mode status
  maintenance:repair                     repair this installation
  maintenance:repair-share-owner         repair invalid share-owner entries in the database
  maintenance:theme:update               Apply custom theme changes
  maintenance:update:htaccess            Updates the .htaccess file

db
  db:add-missing-columns                 Add missing optional columns to the database tables
  db:add-missing-indices                 Add missing indices to the database tables
  db:add-missing-primary-keys            Add missing primary keys to the database tables
  db:convert-filecache-bigint            Convert the ID columns of the filecache to BigInt
  db:convert-mysql-charset               Convert charset of MySQL/MariaDB to use utf8mb4
  db:convert-type                        Convert the Nextcloud database to the newly configured one
  db:schema:expected                     Export the expected database schema for a fresh installation
  db:schema:export                       Export the current database schema
  maintenance:mimetype:update-db         Update database mimetypes and update filecache