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 with GlusterFS on CentOS 7

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 CentOS 7 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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KVM OpenStack Error: /Stage[main]/Nova::Db::Sync/Exec[nova-db-sync]

Packstack Error: Command exceeded timeout
Few times during KVM based OpenStack (Mitaka, Newton) automated installations using packstack we encountered DB synchronization errors.

It turned out, that these installation errors appeared due to slow network and/or poor hardware performance of KVM virtualized hardware used to build OpenStack virtual nodes (Controller, Network, Compute).
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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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