Here is a quick one. When trying to perform a database backup with mysqldump I received this error:
mysqldump: Got errno 11 on write.
I could find no references to this error number or a list of mysqldump error numbers. You would think mysql would release this list else what is the point of showing a number.
Anyway, I created a new folder and gave permission to everyone (chmod 777) and ran the mysqldump to place the backup file in that location and it worked so it appears to be a permissions issue.
Hope this helps