Several people have reported upgrades failing when moving from 2.6.x to 2.7. We need to investigate this issue and work out why it is happening. Note that server ID was introduced in 2.5.5, so all 2.6.x instances should have a server ID.

2008-01-28 14:15:14,541 ERROR main com.atlassian.upgrade.AbstractUpgradeManager doUpgrade Upgrade failed: null
java.lang.NullPointerException
at org.apache.commons.codec.digest.DigestUtils.md5(DigestUtils.java:86)
at com.atlassian.confluence.security.trust.ConfluenceTrustedApplicationsManager.getAliasForSid(ConfluenceTrustedApplicationsManager.java:166)
at com.atlassian.confluence.security.trust.ConfluenceTrustedApplicationsManager.getSystemAlias(ConfluenceTrustedApplicationsManager.java:160)
at com.atlassian.confluence.security.trust.ConfluenceTrustedApplicationsManager.getCurrentApplicationInternal(ConfluenceTrustedApplicationsManager.java:1
40)
at com.atlassian.confluence.security.trust.ConfluenceTrustedApplicationsManager.getCurrentApplication(ConfluenceTrustedApplicationsManager.java:101)
at com.atlassian.confluence.security.trust.ConfluenceTrustedApplicationsManager.initConfluenceKey(ConfluenceTrustedApplicationsManager.java:172)

The query to check your database for a server ID is:

select * from bandana where bandanakey like 'confluence.server.id';

Note: You should not make public your server ID or put it on this issue. It is used to verify your identity with Atlassian.