=== Opened files - directories ===
<sxh bash>
lsof /var/log/httpd/
</sxh>
\\
=== Opened files - processes ===
<sxh bash>
lsof -c ssh
</sxh>
\\
=== Opened files - device busy ===
"Device or Resource Busy" Error - we need to find out what are all the processes using the mount point and kill those processes to umount the directory. 
\\
By using lsof we can find those processes.
<sxh bash>
lsof /home
</sxh>
\\
=== Opened files - specific users ===
<sxh bash>
lsof -u luke
</sxh>
== Killing all processes that belong to a user ==
<sxh bash>
kill -9 `lsof -t -u luke`
</sxh>
\\
=== Opened files - specific process ===
<sxh bash>
lsof -p 1234
</sxh>