As you are aware, no service runs alone on some server. You always have to take into account the communication layer between your server and client services. One of the most tricky thing a lot of people overlook is the “housekeeping” of the communication layer. In a properly setup enterprise environment your communication layer (firewalls,… Read More »
Following is a simple and easy way to do a consistent back-up of the /home directory (usually mounted in a separate partition) on a running system. We do not have the luxury of being able to stop the operations of a server and unmount the home partition to make sure no changes are done during… Read More »
Sometimes really simple questions are hard to answer. One day I got the question from a coworker: “How do I know if some installed RAM is ECC or not”. The easiest way is to use dmidecode command that dumps in Linux all the system characteristics. But because I had no idea how to see if… Read More »
Sometimes you get a CA certificate in DER format and some application requires it in a PEM format. OpenSSL to the rescue: # openssl x509 -inform der -in myCA.der -out myCA.pem
When running complex environments on Docker on Linux again we face the mighty selinux. There are plenty of selinux alerts generated when I start my environment when the host machines have selinux enabled and volumes are used by the containers. Setting selinux permissions is hard and tedious and many people just prefer to disable it.… Read More »
There is a very simple way to save a pdf presentation to individual jpeg images of the slides using convert. convert -density 300 presentation.pdf presentation_page_%04d.jpg where: – density 300 specifies the DPI used to read the pdf. – presentation_page_%04d.jpg is a name pattern for the saved images As a result if presentation has 20 slides… Read More »
It seems that now I have a name for what I have doing for the last 15 years 🙂 I attended a a DevTalks conference and the hype of the day was the DevOps idea. According to the wiki definition: DevOps (a clipped compound of “software DEVelopment” and “information technology OPerationS”) is a term used… Read More »
I have a RHEL 6 Linux cluster setup where the main database storage is replicated on a remote site using DRBD. In case of a failure of the primary site the decision is taken to move operations on the remote site. When the production site is back online sometimes the administrator is too eager to… Read More »
In a Linux HA cluster setup on RHEL 6 that involves replication between sites using DRBD suddenly after reboot of one of the nodes it was imposible to start any cluster service from that node. Surprinsingly there was no issue to do so from the other node. While looking in the /var/log/messages on the affected… Read More »
Sometimes weird things happen when selinux is activated and files are un-tagged or policies are missing. Because I do not want to apply the usual stupid Internet advice: “disable selinux” I am trying to fix it if possible. Two simple steps to alleviate some of the “issues” caused by selinux. STEP 1: Generate SELinux policy… Read More »