High Availability Apache Galera Cluster with HAProxy Load Balancer


Using a high-availability LAMP (Linux Apache MySQL/MariaDB PHP) server may totally eliminate the risk of server’s downtime, which can be crucial in case of a production HTTP server, serving critical business application. We can set a redundant, fully functional, high-avalability production HTTP server for free, using well known and proven technologies like Apache server, MariaDB/Galera cluster software and HAProxy load balancer.
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Install Nextcloud with Docker on Debian 10 Buster

nextcloud docker installation on debian buster
Nextcloud is a lightweight, open-source StaaS (Storage as a Service) platform, written i PHP and JavaScript, which provides file sync, file sharing and creative collaboration services. The software can be installed on local hardware as a perfect alternative for commercial StaaS solutions like Dropbox, OneDrive, Hightail, etc…
Nextcloud is a typical LAMP (Linux Apache MySQL PHP) software, but instead of ardous and problematic LAMP environment installation and file sharing platform implementation, we can deploy a turnkey Nextcloud platform in just a few minutes, using Docker containers, preferably with docker-compose.

In this article I am launching Nextcloud platform in two Docker containers: nextcloud and mariadb which use local Docker volumes as a file and database storage. This solution will enable us to quickly and painlessly upgrade our Nextcloud to a newer versions in future.
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OpenStack Pike TripleO Overcloud Deployment using VLAN based Network Isolation

OpenStack Pike TripleO Overcloud Deployment with Network Isolation
The basic OpenStack TripleO deployment utilises the so called provisioning / control plane network for all types of traffic (internal API, tenant, storage, storage management, etc…), that run across the whole OpenStack installation. The Undercloud node, which is used for Overcloud deployment, becomes a kind of a gateway for Overcloud nodes to the external network. This solution has a major disadventage: the single point of access which is here the Undercloud node, can quickly turn into a single point of failure, if Undercloud fails, cutting us out from Overcloud nodes. Moreover, any diagnostic steps, in case of network issues, bottle necks, etc., become more difficult , since all the traffic runs in one big tube, which is provisioning / control plane network.
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Kickstart Tutorial – Practical Examples for RHEL 7 / CentOS 7

Yum – find out which RPM package provides particular file or command
Linux installation can be performed totally unattended using Kickstart file, which contains configuration, required setup and post installation tasks to fully automate installation process without being prompted for any input details. Kickstart file can be placed in the remote repository or can be included in ISO image in order to be read by Anaconda installer during system installation.

In this tutorial we present some practical solutions that can be placed in kickstart file to automate CentOS 7 / Red Hat 7 installation tasks.
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Extending Minimum Time Between IPMI Operations in OpenStack Ironic

Extending Minimum Time Between IPMI Operations in OpenStack Ironic
In TripleO based installations of OpenStack the deployment of Overcloud nodes is coordinated by so called Ironic module, which was developed in general to deploy OS on bare metal servers. There is a number of IPMI (Intelligent Platform Management Interface) drivers supported by Ironic, like pxe_ilo for HP Proliant Gen8+, pxe_drac for DELL 12G+, ipmi for generic servers, etc… In case of the generic ipmi driver, Ironic script, which is installed on undercloud (or OSP director), uses a Linux command line ipmitool to send IPMI messages to the Overcloud nodes to control them during TripleO deployment.
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OpenStack Pike TripleO Undercloud and Overcloud Deployment on 3 Bare Metal Servers

OpenStack Pike TripleO Undercloud and Overcloud Deployment on Bare Metal
Nowadays Packstack based OpenStack installations are used for proof-of-concept and demonstration purposes only. The official RDO community points TripleO (OpenStack On OpenStack) as a recommended OpenStack deployment method for production cloud. TripleO is an automated installation tool, based on Ironic OpenStack node provisioning software, intended for deployments on bare metal servers, that is, on physical hardware. TripleO generally requires using servers equipped with BMC (Baseboard Management Controller) or IPMI (Intelligent Platform Management Interface) modules, like HPE iLO (integrated Lights Out) in order to be able to manage and controll servers during OpenStack deployment, maintenance and node introspection procedures.
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Enable UEFI for QEMU KVM on Fedora

Enable UEFI for QEMU KVM on Fedora
UEFI (Unified Extensible Firmware Interface) has become a successfull successor of an outworn and obsolete BIOS firmware. Emulating UEFI based hardware on KVM/QEMU Virtual Machine is possible thanks to so called OVMF (Open Virtual Machine Firmware), which comes from EDK2 (EFI Development Kit), UEFI reference implementation. OVMF is available as an RPM package for RPM based distros (CentOS, Fedora, Red Hat). In case of Fedora release all we need is edk2-ovmf RPM package.
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How to configure Docker Proxy on CentOS 7, RHEL 7

How to enable Proxy for Docker engine with or without authentication on CentOS 7, Red Hat Enterprise Linux 7?

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CentOS 7 Installation with LVM RAID 1 – Mirroring

CentOS 7 installation with LVM RAID 1 mirroring
CentOS 7 may offer us a possibility of automatic RAID configuration in Anaconda installer, that is during OS installation, once it detects more than one physical device attached to the computer. Mentioned RAID is generally the LVM-RAID setup, based on well known mdadm – Linux Software RAID. It’s a pretty convenient solution, since we don’t need to setup RAID manually after installation, on already running system.

The below procedure presents CentOS 7 testing installation with LVM RAID 1 (Mirroring) on KVM based Virtual Machine with two attached 20GB virtual disks.
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MariaDB high CPU usage in OpenStack Pike

MariaDB High CPU usage in OpenStack Pike
Testing OpenStack Pike after Packstack based deployment I realised MySQL daemon was utilizing 100% CPU resources without any specific reason, but I had never faced such problem before in previous OpenStack releases. The problem also has never appeared during my TripleO based OpenStack Pike deployments, so looks like it’s strictly Packstack related issue.

The situation heppened on few bare metal installations on pretty powerful servers. Restarting mariadb service was helpful just for the first few minutes after service restart, then the problem would happen again and again, what resulted in frequent Horizon Dashboard and Keystone inaccessibility and partial Controller unavailability.
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