JIRA Cannot Start Due to 'unable to clean the cache directory: /opt/jira/plugins/.osgi-plugins/felix'

Symptoms

After restarting JIRA, the following error appeared:

                        JIRA Startup Failed
You cannot access JIRA at present. Look at the table below to identify the reasons
 
Description
Unable to clean the cache directory: /opt/jira/plugins/.osgi-plugins/felix

Cause

There are two known causes for this issue:

The inconsistency of OSGI plugin caches triggered from inappropriate shutdown of Tomcat.
The Tomcat user does not have the correct permissions to access the directory.

Resolution

Stop JIRA.
Remove the folder specified within the UI, for example:
```
$JIRA_HOME/plugins/.osgi-plugins/felix/
```
This will be rebuilt upon JIRA startup.
Ensure that the Tomcat user has the correct permissions, as in our JIRA Generates a FileNotFoundException due to Permission denied KB article.
Start JIRA.
Normally this is a one-time error. If it repeats, see JIRA Does Not Terminate after Shutdown Script.

We have a bug that is being tracked for this behaviour under

JRA-27438 - JIRA fails to start if it can't delete the Felix OSGI cache OPEN - please vote and watch it for future updates from our developers on a permanent solution.