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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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:
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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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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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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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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