Install and configure DKIM with Postfix on RHEL7

Introduction DKIM (Domain Keys Identified Mail) is a measure against email spoofing, Phishing and SPAM mails. Its easy to implement as you will learn in this article. DKIM signs emails on the outgoing SMTP server, the receiving SMTP can verify the signature by looking up the mail._domainkey TXT DNS record of the respective domain to check if the email originates from that domain or if it is forged. This howto can be used to implement DKIM on a SMTP server ….Read More

Migrating from CentOS7 to RHEL7

There are various reasons why to migrate from CentOS to RHEL. Quicker access to bugfixes and new minor releases as well as having a fully commercially supported system. There are different tutorial on the net how to migrate from RHEL to CentOS but almost no information about the other way round. It is quite simple and at the end of the day you have only Red Hat Packages installed. In 2012 I wrote an article about Migrating from CentOS6 to ….Read More

Building a virtual CEPH storage cluster

This post will guide you trough the procedure to build up a testbed on RHEL7 for a complete CEPH cluster. At the end you will have an admin server, one monitoring node and three storage nodes. CEPH is a object and block storage mostly used for virtual machine images and bulk BLOBS such as video- and other media. It is not intended to be used as a file storage (yet). Machine set up I’ve set up five virtual machines, one ….Read More