CentOS Remove Old Kernels

Tonight when upgrading a CentOS Linux server it was noted by YUM that 15MB more disk space was needed to upgrade grub and the kernel itself. Below are four quick steps to verify what kernels are installed, install yum-utils if it is not installed already, delete previous kernels and set YUM to remove old kernels…

Technology Insights

cut – Represent A Tab As The Delimiter With Linux cut Command

I have been using the cut command a lot recently to shed extra data from large text files. I typically use cut with a specific delimiter by activating the -d switch and I thought that the -d switch was required. It turns out that -d is not required and by default -d actually defaults to the delimiter being a tab. When you need to have a tab as the delimiter for cut you simply don’t specify the -d switch. Below I show a couple examples of a file trimmed down using cut with and without the -d switch as well as another way to convert tabs in a file to spaces which then will allow you to use the Linux cut command with the -d” ” switch.

Technology Errors

vsftpd: pam_listfile(vsftpd:auth): Refused user root for service vsftpd

If you are attempting to FTP to a server running vsftpd as its FTP daemon you will be refused if this is a default vsftpd installation. It is strongly recommended to not allow root access to FTP because of security concerns which would provide the ftp user access to destroy anything on the server running FTP at will. Regardless it might be necessary for specific tasks and the below information will assist you in configuring vsftpd to allow the root user to login.

Technology Insights

Linux Create Fake Ethernet Interface

There could be numerous reasons to create a fake Ethernet interface on a Linux server though I have heard that people might do so to get around licensing of software that is tied to the MAC address of a specific Ethernet port. You really just enable a dummy Ethernet interface and assign the MAC address to it which is explain in more detail below. The easiest way to do this is to simply assign a MAC address to an Ethernet interface you are not using on your server where the drivers have already been installed automatically. If you do not have a spare Ethernet interface then the instructions below will assist you to accomplish your goal.

Technology Errors

Fast Secure Contact Form Error – Could not read CAPTCHA token file. Try again.

After upgrading the Fast Secure Contact Form plugin for WordPress you should definitely test to make sure things are working properly because you likely will receive an error when submitting the contact form if you are using the built in captcha. The error which is explained in more detail complains of not being able to read a token file. Below we describe how to quickly resolve the Fast Secure Contact Form captcha error.