Blog Grid

How to add Hot Spare Volume to the existing mdadm software RAID array

Having a Hot Spare significantly increases the security of our data in a RAID array. In the case of a single disk failure, a Hot Spare jumps in the place of a faulty drive. Working as a temporary replacement, a Hot Spare can potentially buy time for us before we swap the faulty drive with the new one.

In the below scenario we have an example CentOS 7, installed on top of RAID 1 (mirror) using mdadm software RAID. The array was created by the Anaconda installer script during OS installation, for more details refer to:
CentOS 7 Installation with LVM RAID 1 – Mirroring.
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Configure VLAN tagged interface over LACP bond on CentOS / RHEL

In one of my previous articles I presented how to:
Configure a bridge interface over a VLAN tagged bonded interface on CentOS / RHEL

This is a supplement to the above tutorial – sometimes all you need is to configure just a regular interface over a VLAN tagged bond and the below procedure describes how to do it on CentOS 7 / RHEL 7 in few easy steps.
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Configure a bridge interface over a VLAN tagged bonded interface on CentOS / RHEL

Linux enables us to create advanced network setups which provide us with special features like NIC Bonding, VLAN tagging or Bridging allowing us to increase network connectivity efficiency and reliability of Linux based hosts.

Linux Bond is a kernel module which facilitates combining multiple network interfaces (like ens1f0, ens1f1) into aggregated links named Bonds to provide network redundancy, link failover and increased throughput.

VLAN tagging (802.1q) helps us to distinguish particular VLANs from network trunk (VLANs range) coming from the switch. It’s very helpful Linux kernel module, which enables us to connect to the multiple networks, if the server has less NICs than networks.
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Install and Configure Checkmk on CentOS 8 and Monitor Linux Hosts using Checkmk agent

If you have important production servers or critical services in your network, having monitoring tools becomes a must. In case of any hardware or software failures, it is crucial to get alerted as soon as possible and take appropriate actions to fix the failure.
In this article I would like to take a look at checkmk – a powerful monitoring software, developed by tribe29 GmbH with tons of configuration options and a user-friendly WebGUI, which can help you fully automate monitoring activities of your hardware and operating systems.
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Configure Postfix SMTP Relay (Smart Host) on CentOS 8

Postfix is a Mail Transport Agent (MTA), which can be easily configured as a private relay host, passing mail to other mail servers. Unlike Sendmail, Postfix is considered a very secure MTA, offering a high level of flexibility and ease of administration.
In this article, I am configuring Postfix on CentOS 8, running on CinderCloud VPS, as SMTP smart host (relay host) using SASL authentication to send out mail further to the OVH mail server.
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Configure Sendmail MTA on CentOS 8 to work as SMTP Relay

Sendmail is easy to implement, lightweight electronic Mail Transport Agent (MTA), which enables you to automate the process of sending e-mail messages from your Linux host. It can play a significant role as a background mechanism for processing outbound emails from monitoring software to deliver status notifications to the system administrators or send diagnostic information at a specified time schedule.
In this article, I present how to install and configure Sendmail on CentOS 8 to work as SMTP Relay for outbound traffic to the OVH mail server.
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