How to shrink OpenStack qcow2 image using qemu-img

shrink openstack qcow2 image
If you transfer qcow2 images very frequently across OpenStack Clouds or between KVM and Openstack environments, they can quickly grow larger. Luckily qcow2 image size can be decreased to reasonable values using qemu-img tool. Below we present how to shrink Openstack/KVM qcow2 image.
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Download Kali Linux OpenStack KVM qcow2 image by tuxfixer.com

Kali Linux Openstack KVM qcow2 image by tuxfixer.com
Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing. Kali Linux can run natively when installed on a computer’s hard disk, can be booted from a live CD or live USB, or it can run as KVM virtual machine or OpenStack instance using qcow2 image.

We have generated Kali Linux OpenStack / KVM 64bit qcow2 ready to use image based on Kali Linux ISO with pre-installed cloud-init package.
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virt-what: Check if your remote server runs in virtual environment

virt-what - detect if we are running in a virtual machine
Have you ever wondered if the server you bought at the hosting provider is in fact a dedicated server or just a VPS and what is the underlying virtualization environment your server runs on?
virt-what provides us the ability to detect if we are running in a virtual machine or on bare-metal (real hrdware). virt-what detects common types of virtualization: hyperv, kvm, openvz, qemu, virtualbox, vmware, xen, etc…
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Scan Remote Host for Open Ports using nmap Port Scanner

Extend LVM Volume Group
nmap (Network Mapper) is an open source tool for network exploration and security auditing and a powerfull port scanner. It can be used locally on localhost as netstat alternative, but it’s main use case is to scan remote hosts for open ports, system type, running services, etc…
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Linux cp mv overwrite without prompt (disable interactive mode)

Linux cp mv disable prompt
Some Linux distributions (for example: RedHat) have aliases configured in the system, especially for root user, which modify basic command line operations like: cp, mv by adding “-i” parameter to prevent user from accidental overwriting or deleting files (interactive mode). This can be disturbing, especially when we are dealing with many files at a time. To get rid of this issue we can modify aliases in the system to disable interactive mode.
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Configure OpenStack Instance at boot using cloud-init and user data

onfigure OpenStack Instance at boot using cloud-init and user data
OpenStack Instance operating system can be configured right after the Instance boot using cloud-init package and user data mechanism. For example we can inject a configuration file to the Instance to set some system variables, set hostname or install a package upon Instance boot time. cloud-init supports few input formats of user data, for example: BASH scripts or cloud config files.
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OpenStack: Create Instance Snapshot to backup or migrate Instance

openstack: create instance snapshot to migrate or restore instance
OpenStack Snapshots can be utilized to backup Instance before some critical changes are made on Instance OS or to migrate Instance to the new OpenStack Cloud.
In this tutorial we will create snapshot from existing Instance to launch it in different Cloud, but you can also create snapshot just to backup the Instance and restore it’s state later in the same Cloud, if needed.
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