OpenStack: How to Manually Delete Orphaned Neutron Port

From time to time, especially during testing and automated script tenant deployment, my OpenStack cloud installation gets disordered. Situations when I am unable to delete neutron port in Horizon dashboard are pretty common phenomenon, this most likely leads to problem with deleting network which the problematic port belongs to.
In such cases we may need to edit OpenStack database, which is MariaDB, and manually delete orphaned neutron port related record from MariaDB ports table.

Error: Failed to delete port
Error: Failed to delete port: Port d06e19fc-c637-402b-85a2-3519c69a1035 has owner network:router_interface and therefore cannot be deleted directly via the port API.

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GlusterFS Storage Setup on Two CentOS 7 Servers and Client

GlusterFS is a simple and easy to configure scalable network attached storage. GlusterFS is a distributed storage consisting of nodes (servers including storage bricks), which export their own local file system as a volume. Volumes can be mounted on client servers as a network storage using NFS and Gluster Fuse. GlusterFS provides failover, redundancy and anti split-brain mechanisms that act as a High Availability system, that’s why in many aspects it is similar to the well known clustering software like Veritas Cluster Suite.

In this tutorial we will install GlusterFS on two CentOS 7 based nodes. We will use KVM Virtual Machines to make things easier and faster, but our main intention is to show you how to install GlusterFS on physical hardware.
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Convert qcow2 to raw image and raw to qcow2 image

qemu-img is a QEMU disk image utility, which allows us to create, convert and modify images offline. It can handle all image formats supported by QEMU (including qcow2 and raw image format).
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Edit qcow2 or raw image files offline using virt-edit

Sometimes I need to edit files inside qcow2 or raw image, but for some reason I don’t want to launch the image in KVM or in Openstack cloud. The image can be edited offline using virt-edit tool.
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Upgrade from Fedora 21 to Fedora 22 using DNF

Starting from Fedora release 21 (Twenty One), Fedora can be upgraded using DNF system upgrade, which is recommended upgrade method for Fedora 21 and later releases. DNF is a kind of successor for FedUp (FEDora UPgrader), which is now obsolete, not supported any more by Fedora Project and should not be used in any circumstances.

In this article we will upgrade Fedora release 21 (Twenty One) to Fedora release 22 (Twenty Two) in five simple steps, using DNF system upgrade method.
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How to Install Docker on Fedora 23

Docker is a software which automates the deployment of applications inside Linux containers, by providing an additional layer of abstraction. This guarantees that it will always run the same, regardless of the environment it is running in. Docker uses the resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent containers to run within a single Linux instance, avoiding the overhead of starting and maintaining virtual machines.

In this tutorial we will setup and launch Docker software on Fedora 23 (64-bit) release.

Prerequisites for Docker installation on Fedora release:
Fedora version: Fedora 22 (64-bit) or higher
kernel version: 3.10 or higher
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