Ok, this is a nightmare, when you found out you did something unknown and break your OpenVAS and every time you tries to start a task, you get a 503 - Service temporarily down message. And whatever you do, its not recovering. Most likely you would go reinstall the whole OpenVAS 8. The real issue is that it takes too long to get everything setup, especially if you want EVERYTHING to be ready and good to go. I know, i have been there.
503 - Service temporarily down
The issue started when i trying to figure out why scan result isn't working for me. I accidentally updated the cert and everything just go down hill from there. Hence, the only way is to figure out what happen. And the following solution seems to work for me.
openvas-mkcert-client -n om -i openvas-nvt-sync --wget /etc/init.d/openvas-scanner stop; /etc/init.d/openvas-manager stop; openvassd rm /var/lib/openvas/mgr/tasks.db openvasmd --progress --rebuild -v
What this does is to remove ALL your task. And rebuild it again. It seems that somehow when we refresh the cert, all the task that bind with the old cert can't seems to perform a handshake with the new cert that i have generated. Hence, removing everything and redo it again seems to solve this problem.
**** UPDATES 20/12/2015 ****
Apparently, Michael Meyer saw this article and somehow added and correctly provided alternative as show below,
"Updating Scanner Certificates If you have changed the CA certificate used to sign the server and client certificates or the client certificate itself you will need to update the certificates in Manager database as well. The database can be updated using the following command: $ openvasmd --modify-scanner <uuid> \ --scanner-ca-pub <cacert> \ --scanner-key-pub <clientcert> \ --scanner-key-priv <clientkey> Where: <uuid> refers to the UUID used by OpenVAS Manager to identify the scanner; the UUID can be retrieved with "openvasmd --get-scanners" <cacert> refers to the certificate of the CA used to sign the scanner certificate <clientcert> refers to the certificate Manager uses to authenticate when connecting to the scanner <clientkey> refers to the private key Manager uses to authenticate when connecting to the scanner"
For more information and other options do go to https://wald.intevation.org/svn/openvas/trunk/openvas-manager/INSTALL where you would find more options and may be helps to resolve your issue.
All credits goes to Michael Meyer and thanks for the update!