Restore a backup
Stop the services. The last one of course only if installed.
root@cloudserver:~# systemctl stop seahub
root@cloudserver:~# systemctl stop seafile
root@cloudserver:~# systemctl stop mysql
root@cloudserver:~# systemctl stop nginx
Remove the current stuff you want to get rid of. Be sure to save anything you want to keep from the current installation like letsencrypt logfiles a.s.o.
root@cloudserver:~# rm -rf /etc/systemd/system/{seafile,seahub}.service /etc/nginx /etc/letsencrypt /opt/Seafile/Server /var/lib/mysql /var/log/letsencrypt /var/log/nginx
Restore a backup:
root@cloudserver:~# tar -C / -xzf /srv/Backup/SeafileInstall/SeafileInstall201707161242.tgz
Reboot the server.