Warning: You have logged in into the Nextcloud container as root user.
See https://github.com/nextcloud/all-in-one#how-to-run-occ-commands if you want to run occ commands.
Apart from that, you can use 'sudo -E -u www-data php occ <your-command>' in order to run occ commands.
Of course <your-command> needs to be substituted with the command that you want to use.