Building a Postfix-based mail system for incoming and outgoing email, capable of successfully sending one million emails per day

It was necessary to build an updated mail system for a client which would handle all incoming and outgoing email, and which could handle successfully sending out an average of one million emails per day. This was based on Postfix, since Postfix is known for reliability, robustness, security, and relative ease of administration. Building a Postfix mail system capable of handling so many emails is quite a significant aim at a time when establishing a positive reputation for independent mail servers delivering high volumes of email is quite a challenging goal.

Continue reading “Building a Postfix-based mail system for incoming and outgoing email, capable of successfully sending one million emails per day”

Security hardening on CentOS 7, Red Hat Enterprise Linux 7 & Amazon Linux

A few years ago I wrote a quite popular post for security hardening on Ubuntu 14.04, and now here’s a new version for CentOS 7 and RHEL 7. Much of it should apply to CentOS/RHEL versions 6 and 8, with some tweaks required here and there. It should also largely work with Amazon Linux and Amazon Linux 2, although again some tweaks will be required for those.

Continue reading “Security hardening on CentOS 7, Red Hat Enterprise Linux 7 & Amazon Linux”

68 very useful CLI commands for SysAdmin & DevOps

For a long time I’ve maintained a memory aid in the form of a list of useful commands which can be used on the command line for Linux, macOS (OS X), BSD, Solaris, etc., so I thought I’d list them in a sticky blog post in case they come in useful for others. Most of these will run on any Unix-type operating system, though I’ve usually indicated where a command is OS-specific. These can be run manually for admin purposes and also scripted for automation purposes.

Continue reading “68 very useful CLI commands for SysAdmin & DevOps”

SysAdmin fame at last!

I was interviewed for a careers feature in the esteemed PC Pro magazine, and my article has been printed in the latest edition:

Matt Brock - Linux system administrator

I think they’ve done a great job of editing my original monologue into a compelling description of the excitement, challenges and rewards of administering computer systems and managing infrastructure, and I hope it helps to encourage college graduates and other potentially interested individuals into the field of system administration.

In the meantime, I’ll continue to enjoy my fifteen minutes of fame…

Virtualisation with KVM and LVM on CentOS 6 via the command line

I’ve found plenty of articles out there explaining how to use KVM with graphical GUI tools. On most of the CentOS servers I administer, however, I use Kickstart to create a customised and minimal GUI-free install to keep things as simple and efficient as possible. Here, therefore, are some guidelines for how to set up a virtualisation environment and virtual machines using KVM on CentOS 6 via the CLI.

Continue reading “Virtualisation with KVM and LVM on CentOS 6 via the command line”