If the occ owncloud command line throws exceptions it could be that you are missing php-pdo-sqlite on your machine. sudo apt-get install php7.4-cli php7.4-fpm php7.4-bcmath php7.4-curl php7.4-gd php7.4-intl php7.4-json php7.4-mbstring php7.4-mysql php7.4-opcache php7.4-sqlite3 php7.4-xml php7.4-zip
put ownCloud in maintenance mode: edit /var/www/owncloud/config/config.php and change this line: 'maintenance' => false, to 'maintenance' => true, bash# cd /var/www/owncloud/data bash# sqlite3 owncloud.db sqlite> DELETE FROM oc_file_locks WHERE 1; sqlite> exit; then edit /var/www/owncloud/config/config.php and change this line: 'maintenance' => true, to 'maintenance' => false, https://central.owncloud.org/t/file-is-locked-how-to-unlock/985