While reviewing the logs of my OpenVPN server recently, I noticed a series of suspicious looking entries that indicated that it was being used as part of a UDP reflection attack. Thankfully this is pretty straightforward to block using the built in functionality of OpenVPN and/or firewall software such as nftables. I'll cover both approaches here.
If you're working on or debugging a PHP application that creates files in the /tmp directory then you may find yourself needing to check for the existence of or the content of these files. On RHEL/CentOS 6 and below this would be as straightforward as listing the contents of /tmp or opening the file in your preferred text editor. On RHEL/CentOS 7 however you may be surprised to see that while your application can see its files fine, you can't.
