The Yum Priorities plugin can be used to enforce ordered protection of repositories, by associating priorities to repositories.

The priorities plugin is a useful tool if properly configured, and used with an understanding of the functionality and a recognition of the limitations and potential issues. It can be used in conjunction with the ‘exclude’ and/or ‘includepkg’ options, as well as the ‘enabled=0′ option to disable a repo by default. This can let you choose which packages a less important repo will supersede those of a more important one.

Install Yum Priorities

# yum install yum-priorities

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It is important for systems administrators to make sure that mission-critical servers are always using the correct system time.

The ntpd (Network Time Protocol daemon) program is an operating system daemon which sets and maintains the system time of day in synchronism with Internet standard time servers. Make sure that the time zone configuration of your computer is correct. ntpd itself does not do anything about the time zones, it just uses UTC internally.
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This tutorial is intended for system administrators wanting to install Varnish on CentOS 6. The reader should know how to configure a web server or application server and have basic knowledge of the HTTP protocol. Once finished the reader should have a basic Varnish cache up and running with the default configuration.

Varnish is a web application accelerator. You install it in front of your web application and it will speed it up significantly.

Varnish web application accelerator homepage: https://www.varnish-cache.org
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In this tutorial we’ll be covering the very basics of installing and configuring Puppet. Puppet is a system for automating system administration tasks. Its automation saves you countless hours of frustration, monotony and reinventing the wheel. It lets you perform administrative task from a central systems to any number of systems running any variant of operating system.

For a more complete description visit Puppet Labs.
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