Category: Linux

How to repair a damage fstab located on an LVM

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

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

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

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

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 »

Fix the CentOS Root Certificate Authority file

For whatever the reason, the /etc/pki/tls/certs/ca-bundle.crt file may get corrupted, in my case, accidentally overwritten.  I could have gone the route of copying the ca-bundle.crt file from another vanilla server, but I wanted a more elegant solution.  There is one, download a new certificate bundle. Download the new certificate bundle.  Since my ca-bundle.crt was overwritten, there was no need to...Read More »

How to Combine Multiple Images Quickly

If you have ever started an eBay auction and wanted to add your large picture collection to it, you will quickly realize that you can only add up to 12 pictures.  While it is true pictures can be added to the body of the auction and linked to an alternate sources, that is extra work. As a work-a-round to the...Read More »

Check if user account is locked in Linux

If you ever needed to know if an account is locked in CentOS Linux, there are a few commands to find those answers. Lock a password using passwd. Additional confirmation that the password is locked.  The double !! indicates that the password is locked.  Note that this user does not have a password. Unlock the password.  Note that the password did...Read More »