I see a lot of 'File name too long' errors in apache error log on Debian.
How can I fix this?
This is a known bug and or known problem.
This could be the bug: https://issues.apache.org/bugzilla/show_bug.cgi?id=45187
Or your file name might actually be too long, in that case, make sure your file-names (or anything between 2 slashes) is not longer then 255 characters.
Also, make sure to revise any mod_rewrite-rules you have, they can also cause this behavior.
When you have an argument/filename longer then 255 chars, apache will check this against your file system limits.
More info on the max filename length can be found here: http://en.wikipedia.org/wiki/Comparison_of_file_systems#Limits
There aren't a lot of them that allow for longer file names, so you will have to make them shorter, no other way around them.
With path too long error I use an alternative tool "Long Path Tool" a guaranteed fast and easy fix.