Author: Grzegorz Juszczak

Extend LVM Volume Group with the new Hard Disk

Extend LVM Volume Group
One of the benefits of LVM (Logical Volume Manager) is the possibility to extend LVM based storage by adding new Physical Volumes which together form LVM Volume Group. Adding new Physical Volume increases the capacity of the whole Volume Group by the capacity of that particular Physical Volume and can be performed online without any outages in LVM activity.
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Backup and Restore Logical Volume using LVM Snapshot

Backup Restore LVM using Snapshot
LVM (Logical Volume Manager) gives us the ability to create Snapshots. LVM Snapshot is a logical volume that temporarily preserves the original data of changing logical volume, so it’s data can be backed up preserving consistency. Snapshot must be created prior to any critical modifications on the Logical Volume in order to fulfill it’s role.

Note: Snapshot Volume needs to be large enough to store the data that will change while it exists. If more data changes than the Snapshot can hold, the Snapshot will become unusable. That means we have to “predict” how much data will be changed on the original Volume while the Snapshot exists to let the Snapshot hold all those data changes.
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Install Nagios Core from RPM on CentOS 7 / RHEL 7

nagios_logo
Nagios is a free software, which offers monitoring and alerting services for servers, switches, applications and services.

This tutorial describes simple Nagios Core and Nagios Plugins installation from rpm packages on CentOS 7 / RedHat 7. There is no need to configure and compile Nagios Core tar.gz based source files unless you really need the newest version.
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OpenStack Kilo 3 Node Installation (Controller, Network, Compute) on CentOS 7

install openstack on three nodes
In this tutorial we will install OpenStack Kilo release from RDO repository on three nodes (Controller, Network, Compute) based on CentOS 7 operating system using packstack automated script. The following installation utilizes VLAN based internal software network infrastructure for communication between instances.

Environment used:
public network (Floating IP network): 192.168.2.0/24
internal network (on each node): no IP space, physical connection only (eth1)
controller node public IP: 192.168.2.12 (eth0)
network node public IP: 192.168.2.13 (eth0)
compute node public IP: 192.168.2.14 (eth0)
OS version (each node): CentOS Linux release 7.2.1511 (Core)
install openstack on 3 nodes
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Register Red Hat 7 using Subscription Manager via Proxy

Register Red Hat 7 using Subscription Manager via Proxy
Once our Red Hat 7 system is installed, it should be registered at RHN using Subscription Manager in order to be able to get newest updates. If the server is placed in network behind firewall and outgoing traffic is blocked by firewall, the only reliable way of keeping our Red Hat 7 up-to-date is through proxy (if any exists).
Below we will show you in 2 simple steps, how to configure HTTP Proxy for Red Hat Subscription Manager and register Red Hat 7 with RHN in command line using HTTP Proxy:
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nethogs – Display Network Utilization per Process

ethernet_card
Have you ever wondered how to check network utilization by PID in Linux? Now it’s easy with nethogs application, which unlike other network utilization monitoring applications (nload, iftop) works like Linux top command, but displays network utilization per PID along with the network device used.

nethogs
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OpenStack: Failed to connect to server (code: 1006)

install openstack on three nodes
In OpenStack Dashboard (Horizon), when I launch an Instance and I am trying to connect to the Instance via Dashboard VNC Console – I am getting error: Failed to connect to server (code: 1006). This is most often caused by improper /etc/nova/nova.conf configuration on Compute node, where the Instance is running:

openstack_vnc_failed_to_connect_to_server_code_1006
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OpenStack: How to Manually Delete Orphaned Neutron Port

openstack
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_logo
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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