Got the same problem in Confluence 7.18.1 running within Docker container :|

This is still present in Confluence 6.3.2. Happened to me on CentOS 7.4 yesterday.

I'm resolving this issue as fixed. The "write to another file first" trick seems to work well enough to prevent us from ending up with empty cfg.xml files: all the linked support cases since we've implemented the fix have referred only to the warning message.

Will file a different issue for that message.

This is still occuring in 2.10.3

The message

 
[atlassian.config.xml.AbstractDom4jXmlConfigurationPersister] saveDocumentAtomically Unable to move D:\confluence\data-2.10.2\confluence.cfg.xml9070676172658464167tmp to 
D:\confluence\data-2.10.2\confluence.cfg.xml. Falling back to non-atomic overwrite.

should now only occur on Windows machines. Unfortunately it is not actually possible to perform an atomic move to an existing file on a Windows operating system (through the File api), and so it will have
to fall back to a non atomic write.
The warning should not be a source of any concern.

Regards,
Andrew Lynch

Error still existant in Confluence 2.10.2:

2009-02-18 20:59:53,527 INFO [Thread-1] [com.atlassian.confluence.lifecycle] contextInitialized Starting Confluence 2.10.2 (build #1518)
2009-02-18 20:59:53,715 INFO [Thread-1] [beans.factory.xml.XmlBeanDefinitionReader] loadBeanDefinitions Loading XML bean definitions from class path resource [bootstrapContext.xml]
2009-02-18 20:59:54,277 INFO [Thread-1] [beans.factory.xml.XmlBeanDefinitionReader] loadBeanDefinitions Loading XML bean definitions from class path resource [setupContext.xml]
2009-02-18 20:59:56,558 WARN [Thread-1] [atlassian.config.xml.AbstractDom4jXmlConfigurationPersister] saveDocumentAtomically Unable to move D:\confluence\data-2.10.2\confluence.cfg.xml9070676172658464167tmp to D:\confluence\data-2.10.2\confluence.cfg.xml. Falling back to non-atomic overwrite.
2009-02-18 20:59:57,730 INFO [Thread-1] [com.atlassian.confluence.lifecycle] init Confluence is ready to serve

Open new issue?

No review necessary, library patch already reviewed.

Quick brain dump. The error message is reasonably harmless. Basically it means that Confluence had to use a slightly unsafe way of writing its main config file. Unless Confluence actually crashes while doing the write, which is very unlikely, everything should be OK.

This message only appears on upgrade because the only information in confluence.cfg.xml that gets updated outside Confluence setup any more is the stored build number, which only changes during upgrades.

The fix to CONFIG-12 (currently in code review) will prevent this error message in most circumstances where it was currently occurring by changing the way we do atomic overwrites of the config file.

From a quick test rig, this happens on Windows when you try and rename across filesystems (C:\something.txt to D:\something.txt).
So CONFIG-12 should fix this problem for Windows too.

CONFIG-12 should make this more reliable on Unix systems, we'll still need to test why/how this happens on Windows