Click for a PDF containing this and four other essential Linux articles. Both of the aliases below will list whatever files are open on your behalf when you are logged in. I suspect that few sysadmins ...

Let's get those errors fixed.

You have probably used lsof from time to time, probably when tracking down some sort of problem. But maybe you haven’t tried all of its permutations or looked at it just to get a deeper understanding ...

Today I was working on a Linux server without lsof. I'd like to know what app is using a certain file. How do I do that? I'm using Red Hat 3.4.6-3 (Linux version 2.6.9-55.ELsmp).

Where does lsof get its port number to port name mapping? I'm running squid proxy cache. I'd like to see lsof reporting it, instead of ndl-aas.