Create USB Boot Disk in Linux using dd command

create usb boot disk using dd utility
Have you ever tried to quickly create USB Boot Disk in Linux and had no dedicated software to create one?
For a long time Linux distributions have come with basic tools like dd utility out of the box. dd command can be used to quickly create USB Boot Disk from the given ISO file without using dedicated tools like unetbootin.
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OpenStack Horizon Error: Unable to get network agents info

OpenStack Horizon Error: Unable to get network agents info
OpenStack Dashboard Error: Unable to get network agents info often seen in Horizon is a result of Neutron related problems.

Usually the problem is caused by neutron-service failure due to service operation time outs.

The below screenshot presents OpenStack Dashboard Error: Unable to get network agents info:

openstack error: unable to get network agents info
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Install and Configure OpenStack Mitaka (CentOS 7) with GlusterFS

integrate openstack with glusterfs storage
OpenStack can use diffirent backend technologies for Cinder Volumes Service to create volumes for Instances running in cloud. The default and most common backend used for Cinder Service is LVM (Logical Volume Manager), but it has one basic disadventage – it’s slow and overloads the server which serves LVM (usually Controller), especially during volume operations like volume deletion. OpenStack supports other Cinder backend technologies, like GlusterFS which is more sophisticated and reliable solution, provides redundancy and does not occupy Controller’s resources, because it usually runs on separate dedicated servers.

In this tutorial we are going to deploy VLAN based OpenStack Mitaka on three nodes (Controller, Network, Compute) using Packstack installer script and integrate it with already existing GlusterFS redundant storage based on two Gluster Peers.

openstack installation and integration with glusterfs
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OpenStack: Unable to Connect to Horizon Dashboard

Packstack Error: Command exceeded timeout
Pretty often after rebooting Controller node or powering it on after shutdown, the Horizon (OpenStack Dashboard) is not responding, but we know that it worked before reboot. This issue may be caused by httpd service (Apache), which entered failed state right after powering on the Controller node.

This results in browser’s connection problem to the Horizon:

chrome_unable to connect
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OpenStack – How to fix Packstack Error: Command exceeded timeout

Packstack Error: Command exceeded timeout
Packstack – the automated OpenStack installer uses Puppet for OpenStack nodes deployment. Packstack, by default, sets timeout for Puppet’s manifests execution to 300 seconds. If you install OpenStack on old hardware, which has poor performance or the nodes are connected to the network with poor throughput, Puppet may encounter execution timeouts when applying it’s manifests across all OpenStack nodes. In other words, Openstack nodes are not able to respond to Puppet (running on Controller node) within the default timeout, this causes Packstack installation to fail.
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How to add user to sudoers – configure sudo access

configure sudo access in redhat
The sudo command offers a mechanism for providing trusted users with administrative access to a system without sharing the password of the root user.
A sudoer (regular user added to sudoers) once authenticated, can execute the administrative commands like they were run by the root user.

In this tutorial we present two examples:

  • How to add regular user to the wheel group and give the wheel group the unlimited root access
  • How to add particular user to the sudoers

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Yum – find out which RPM package provides particular file or command

what rpm provides a file in centos
Have you ever wondered how to find RPM package which contains particular script, application or command in your RedHat / CentOS or any other Yum / RPM based operating system? Have you ever needed to find the RPM package which provides some service or feature?

Yum package manager provides parameters to fast and easy search for particular files / features in Red Hat / CentOS RPM repositories:
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Manage and Configure Kdump Service on CentOS 7 / Red Hat 7

enable disable configure kdump on centos redhat rhel
Kdump is a reliable Kernel Crash Dumping Mechanism, in which a crash dump is captured by a second kernel (crash kernel) booted when the main kernel crashes.

This second kernel (crash kernel) uses a small amount of memory for booting and capturing the dump image (vmcore) file. The part of memory reserved by the main kernel is used by the second kernel to boot. Preserving the main kernel’s crash dump is a result of kexec mechanism which allows to boot the second kernel without the necessity of rebooting the system and passing through BIOS procedures.

The time for capturing the vmcore file depends on the amount of the occupied memory during crash. The average time of capturing a 5GB vmcore file is approximately 20-25 minutes.

When the kdump is successfully made during the system crash, a vmcore file is created in a dump location (usually /var/crash/ directory) and next the system reboots. After crash the vmcore file should be analyzed to determine root cause of the failure.

Below we present how to configure and manage kdump service on CentOS 7 / RHEL 7.
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Setup Puppet Master and Multiple Agents on CentOS 7

install and configure puppet on centos 7
Puppet is an open-source configuration management tool written in Ruby by Luke Kanies which includes its own declarative language to describe system configuration.

In this tutorial we install and configure Puppet on CentOS 7 based hosts.
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Install Xfce 4 Desktop Environment on CentOS 7

install xfce 4 desktop environment on centos 7
Xfce is a free and open-source desktop environment for Unix and Unix-like platforms which aims to be fast, intuitive, user-friendly and lightweight, while still being visually attractive for user.

In the below short tutorial we will install Xfce 4 Desktop Environment on CentOS 7 system in few steps.
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