Our server was accidentally upgraded; can it be downgraded?

admin admin_trokdm

My server is reporting;
Database build number: 800009
JIRA app build number: 712004

The installer was accidentally run on the live system (v7.12.3) for v8.0.1.  And while the installation was cancelled, and the server remaind opreable, it altered the numbers above such that when the system was powered off, the mistake became apparent as the server will not start again with the v7.12.3, nor the v8.0.1.

I want to revert the server to the previous version (7.12.3), and experienced help would be well welcomed.

admin admin_trokdm

Adding this line to the ${JIRA_INSTALL}/bin/setenv.sh file provided what I required, as below;

JVM_SUPPORT_RECOMMENDED_ARGS="-Djira.downgrade.allowed=true"