Explore information related to virtualization

Virtualization Restrictions in RedHat Linux with KVM

This article covers Virtualization Restrictions in RedHat Linux which are additional support and product restrictions of the virtualization packages.


The following notes apply to all versions of Red Hat Virtualization:

1. Supported limits reflect the current state of system testing by Red Hat and its partners. Systems exceeding these supported limits may be included in the Hardware Catalog after joint testing between Red Hat and its partners. If they exceed the supported limits posted here, entries in the Hardware Catalog are fully supported. In addition to supported limits reflecting hardware capability, there may be additional limits under the Red Hat Enterprise Linux subscription terms. Supported limits are subject to change based on ongoing testing activities.


2. These limits do not apply to Red Hat Enterprise Linux (RHEL) with KVM virtualization, which offers virtualization for low-density environments.


3. Guest operating systems have different minimum memory requirements. Virtual machine memory can be allocated as small as required.

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USB device passthrough to Hyper-V - How to get this done

This article covers how to perform Hyper-V USB Passthrough. A USB passthrough is referenced when a keyboard has female USB ports for other devices to be plugged into the keyboard. USB passthroughs requires more than one USB port to be used by the keyboard in order to pass the USB through to the PC, often requiring an additional connection to the host system for powered ports.


What does Hyper-V USB passthrough Mean?

Hyper-V USB passthrough functionality allows you to access the USB device from within a virtual machine. There is a way to enable USB passthrough on Hyper-V for a memory stick, but you’ll have to use Windows storage subsystem.


Known issues with Hyper-V USB device passthrough organized with native methods:

1. Platform restrictions: said methods rely upon Windows storage subsystem so using them to set up Hyper-V USB passthrough on Linux (or any other OS that’s not Windows) is out of question, sadly.

2. An extremely limited list of supported devices: for the native methods to work, your USB peripheral must be recognized as a “Mass Storage Device”. No exceptions.

3. No sharing: once your device is set in passthrough mode, you can access it only from the guest OS. That’s why using these methods to permanently connect a USB to Hyper-V is definitely not the best idea.

4. Poor choice for a cloud: with these methods, the USB device is always locked to a specific host PC while there's no way to anchor a cloud-based Hyper-V guest system or preestimate where it's going to run for your next session.


Advantages of using RDP for Hyper-V USB passthrough:

1. Works for literally any hypervisor you can name;

2. Instant access to USB devices, once RDP connection is up;

3. Group Policy feature for overall control;

4. All USB devices plugged into your host PC are accessible from a virtual machine.


To enable USB device in Hyper-V with the Enhanced Session Mode:

1. On a host computer, you go to the Hyper-V Manager, right-click the name of the host and choose Hyper-V Settings.

2. In the Setting window, you will see the Server and User sections. Select Enhanced Session Mode Policy in the Server section and allow the enhanced session mode by checking the corresponding box.

3. Now, choose "Enhanced Session Mode" in the User section and check the “Use enhanced session mode” box.

4. Click OK and the changes will be saved.


To allow Hyper-V access to attached USB devices:

1. Start the Hyper-V Manager and double-click the name of your virtual machine.

2. In the pop-up window, click “Show Options” to configure your VM’s future connections.

3. After that, go to the tab “Local resources” and click “More” in the section “Local devices and resources”.

4. Then, check the boxes “Other supported Plug and Play devices” and “Devices that I plug in later”. Hit OK.

5. If you want this configuration to be saved for all future connections, check the corresponding box in the “Display” tab. Click “Connect” to implement the changes.

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Create CentOS Fedora RHEL VM Template on KVM - How to do it

This article covers how to create CentOS/Fedora/RHEL VM Templates on KVM. VM Templates are more useful when deploying high numbers of similar VMs that require consistency across deployments. If something goes wrong in an instance created from the Template, you can clone a fresh VM from the template with minimal effort.


To install KVM in your Linux system:

The KVM service (libvirtd) should be running and enabled to start at boot.

$ sudo systemctl start libvirtd

$ sudo systemctl enable libvirtd

Enable vhost-net kernel module on Ubuntu/Debian.

$ sudo modprobe vhost_net

# echo vhost_net | sudo tee -a /etc/modules


How to Prepare CentOS / Fedora / RHEL VM template ?

1. Update system

After you finish VM installation, login to the instance and update all system packages to the latest versions.

$ sudo yum -y update

2. Install standard basic packages missing:

$ sudo yum install -y epel-release vim bash-completion wget curl telnet net-tools unzip lvm2 

3. Install acpid and cloud-init packages.

$ sudo yum -y install acpid cloud-init cloud-utils-growpart

$ sudo sudo systemctl enable --now acpid

4. Disable the zeroconf route

$ echo "NOZEROCONF=yes" | sudo tee -a /etc/sysconfig/network

5. Configure GRUB_CMDLINE_LINUX – For Openstack usage.

If you plan on exporting template to Openstack Glance image service, edit the /etc/default/grub file and configure the GRUB_CMDLINE_LINUX option. Your line should look like below – remove rhgb quiet and add console=tty0 console=ttyS0,115200n8.

GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=cl/root rd.lvm.lv=cl/swap console=tty0 console=ttyS0,115200n8"

Generate grub configuration.

$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg

6. Install other packages you need on your baseline template.

7. When done, power off the virtual machine.


How to Clean VM template ?

You need virt-sysprep tool for cleaning the instance.

$ sudo virt-sysprep -d centos7

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Virtuozzo VS Hyper-V - Which is better

This article covers some comparison between Virtuozzo VS Hyper-V. 

Hyper-V and Virtuozzo are both popular VPS platforms used by a large number of web hosting providers for the provisioning of Windows VPS hosting services, with Virtuozzo being favoured for Windows Server 2003 VPS hosting and Hyper-V being the most reliable solution for Windows Server 2008 VPS hosting services.


Advantages of using Virtuozzo over Hyper-V include:

1. Direct Linux support – Virtuozzo can be installed on their Windows or Linux VPS hosting nodes, and although Hyper-V can be used for the hosting of virtual machines running Linux it is only available for use on Windows Server 2008.

2. Web based control panel (Parallels Power Panel) – the Parallels Power Panel will allow users to manage their Linux or Windows VPS hosting server from a web based interface meaning that if they aren't in a situation where they can access their VPS server via Remote Desktop then they can use the Power Panel to restart their VPS server if necessary or to kill any services or processes which may be overloading their VPS server’s resources.

3. Separate application – the fact that Virtuozzo is a separate application which can be installed on top of the operating system can have its advantages in some cases, for example if a web hosting providers wishes to discontinue using a server for VPS server hosting then all they have to do is uninstall the application from their server, although in most cases it is advised to do an OS reload anyway to ensure that you have a blank canvas to start with.


Advantages of using Hyper-V over Virtuozzo:

1. Cost – with Virtuozzo VPS hosting web hosting providers have to pay for the cost of the Virtuozzo application and the cost of the operating system license, but because Hyper-V is part of the Windows Server 2008 operating system they will only need to pay for the operating system license – this can help to reduce the costs of Hyper-V VPS hosting services and as the cost of the operating system falls, prices will fall further and will eventually meet Virtuozzo Windows Server 2003 hosting services when it comes to price which will mean that people will gradually move over to using Windows Server 2008 VPS hosting.

2. Reliability – as Hyper-V is part of the Window Server 2008 operating system, web hosting providers are able to guarantee reliable Windows Server 2008 VPS server hosting services.

3. Native support for Windows Server 2008 – although Virtuozzo may have support for Windows Server 2008, it hasn’t been able to offer the most reliable of Windows Server 2008 VPS hosting services.

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libvirtd failed to start - Fix it Now

This article covers how to resolve the error 'libvirtd failed to start' which happens while manually trying to start libvirt daemon. 

To resolve this #libvirtd #error, Try journalctl -u libvirtd.service and see if the full log for the service has more information.

You can manually install "libxslt" to resolve the problem.

Also you can try re-installing the packages that libvirtd/KVM requires and did a full system update. 

After that, reboot the server, and libvirtd.service will be working fine.

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oVirt Server unable to upload image to disk

This article will guide you on ways to resolve 'ovirt: unable to upload image to disk' error.

You can upload virtual disk images and ISO images to your data storage domain in the Administration Portal or with the REST API.

QEMU-compatible virtual disks can be attached to virtual machines. Virtual disk types must be either QCOW2 or raw. Disks created from a QCOW2 virtual disk cannot be shareable, and the QCOW2 virtual disk file must not have a backing file.

ISO images can be attached to virtual machines as CDROMs or used to boot virtual machines.


To Upload an Image to a Data Storage Domain:

1. Click Storage - Disks.

2. Select Start from the Upload menu.

3. Click Choose File and select the image to upload.

4. Fill in the Disk Options fields.

5. Click OK.

A progress bar indicates the status of the upload. You can pause, cancel, or resume uploads from the Upload menu.

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Ispconfig vs vestacp

This article will guide you on how to choose the best control panel for customers. Basically, many factors depends to choose the right panel like Ispconfig and Vestacp.

Vesta control panel (#VestaCP) is an open source hosting control panel, which can be used to manage multiple websites, create and manage email accounts, FTP accounts, and #MySQL databases, manage DNS records and more.


To Install And Use Vesta Control Panel:

1. Install SSH Client.

2. Choose The Configuration Panel.

3. Login to Putty and VestaCP Installation.

4. Create a new user.

5. Add a new domain and database.

6. Add Cloudflare nameservers.

7. Add files to your domain via FTP.

8. Repeat the process for all your websites.


ISPConfig is a free open-source control panel application that allows website owners to easily administer their sites, similar to cPanel and Plesk. 

It also allows resellers to manage multiple accounts on multiple physical or virtual servers.

ISPConfig only runs on #Linux servers.


To log into ISPConfig:

Navigate to the URL of your ISPConfig system (e.g. https://www.domain.tld:81 or http://www.domain.tld:81; replace "www. domain. tld" appropriately) with your Browser and enter your user name and your password into the form "Login". Confirm by clicking on "Login".

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OpenStack instance Creation

This tutorial is all about assigning a fixed static IP address in OpenStack by creating ports and adding them to the instance.

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Set up SNMP VMWare ESXi 5 5

This article will guide you on the steps to follow to configure SNMP VMWare ESXi 5.5.

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vCenter installation on ESXi Host

This article will guide you on how to install vCenter Server on a physical server or a virtual machine running Windows.

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Vmware virtual machine disks consolidation is needed error

This guide will help you to fix the warning error experienced in the process of deleting a snapshot, the snapshot VMDK files or logs have not been deleted correctly.

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KVM Installation on CentOS 7

This article will guide you through the process of installing kernel-based virtual machine (KVM) on your CentOS 7 machine.

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