The truncate command

admin • • No Comment
If you ever get in a bind and a log file has gone out of control and your disk space is full, you may be tempted to delete the log file.  There may be a couple of problems with that.  One, the application is still using the file so that delete may not actually take place until the application is...Read More »

Best Practice for chown

admin • • No Comment
Over the years, I have seen a couple of variations with the use of the chown command. The ":" (colon) vs "." (dot).  While studying for the RHEL6 exam sometime ago, the books that I had used each had one or the other in their documentation.  I have read that the posix standard is using chown with the ":" (colon)....Read More »

How to Update a Lenovo BIOS with USB

admin •
Lenovo provides an ISO for CD/DVD burning and an EXE for running the executable from within Windows.  There is NO support for an ISO booting from a USB.  Many modern laptops are ordered without a CD ROM and maybe an extra hard drive in it's place.  Most people use USB sticks for the majority of their effort when the need...Read More »

How to repair a damage fstab located on an LVM

admin •
i made a change to the /etc/fstab that looked perfectly fine until I rebooted the system (CentOS 6) running as a virtual machine.  The system did not start, there was a Kernel panic, and using the single boot mode did not provide any access to the system.  I changed the "/" partition to a UUID number after changing the volume...Read More »

Create a Port Listener to verify connectivity

admin •
How to test an open port without having the application installed.  Suppose you have a situation where you just created a new Linux server (CentOS 6) and you will eventually have an application run on Tomcat port 8080/tcp. You will want this application to use some sort of a Reverse Proxy and this all goes through a firewall that sits...Read More »

Kickstart validation

admin •
Customizing a kickstart file to meet your requirements can be challenging.  One typo or incorrect setting and it simply won't work.  Validation of a success or fail can be achieved with a time consuming reboot.  However, there is a quicker solution. Be certain to validate the kickstart on the same operating system version as the kickstart file or you may...Read More »

Add custom DNS entries to Pi-Hole

admin •
Pi-Hole is the black hole for the internet. As of the most recent Pi-hole Version v2.13.2 with Web Interface Version v2.5.2, a local network should have the necessary tools, DNS and DHCP servers, to run successfully. With that said, what if you want custom DNS settings? I tried this approach successfully, so now one IP resolves to several domain names....Read More »

Add Root Certificates to a CentOS Linux Server

admin •
Adding a root authority certificate to a server that does not already have the cert may be added to the server manually. Install the ca-certificates package: Enable the dynamic CA configuration feature: Add it as a new file to /etc/pki/ca-trust/source/anchors/: Use command: CentOS 7 CentOS 7.0 and later include a shared store for certificate authorities. Read the manual for additional...Read More »