Loadbalancing / failover with IPVS and keepalived

Introduction Correct failover and loadbalancing is crucial for high availablility environment. With proper setup we can eliminate single points of failure in case of server crash. I use linux kernel’s support for load balancing, since that seems as well documented and scalable method. What I want to achieve here, is actually fully redundant architecture, so

Checking limits of a running Linux process – ulimit

If we are dealing with servers that need to handle a lot of concurrent connections, we soon bump limits of our default Linux server installation. In order to be able to further modify these limits, Linux has ulimit. We can set system wide limits on CentOS in /etc/security/limits.conf or manually setting them with ulimit command. We

Testing SMTPS certificate

Sometimes you need to test if your newely installed certificate on mail server actually works and is refreshed. For example when your old one expired and you replaced it. You might even want to write some monitoring scripts to check from remote server, either SSL certificate is about to expire, or isn’t working correctly. For

WinDirStat / KDirStat – Disk usage and statistics program

I noticed my SSD in laptop is almost full. With it’s small size (i only have 80GB sized SSD) I have to constantly keep my files cleaned up in order to maintain free space on it. I use WinDirStat / KDirStat for this task. *DirStat is a disk usage statistics viewer and cleanup tool for

Internationalized domain names (IDN) and DNS / Bind9 problem

To use domain names with special characters ( παράδειγμα.δοκιμή or مثال.إختبار), you need to transform them into proper format. To accomplish that, we use idn command from libidn package. It should be included in base repository so simple: yum install libidn would suffice. To get real name of domain you need to have UTF-8 terminal