The configuration of yum can be divided into multiple files, and repository configurations can include variables such as $basearch or $releasever. The main configuration file for yum is /etc/yum.conf, which contains the global options for yum and can also define repositories in the [repository] sections. However, it is recommended to define individual repositories in separate files in the /etc/yum.repos.d/ directory, which can be easier to manage and maintain. Each file in this directory should have a .repo extension and contain one or more [repository] sections with the repository name, URL, and other options12. Repository configurations can use yum variables to dynamically set values for certain options, such as the baseurl or the enabled. Yum variables are enclosed in curly braces and start with a dollar sign, such as {$basearch} or {$releasever}. These variables are replaced by their actual values at runtime, based on the system architecture, the operating system version, or other factors. Some of the common yum variables are34:
$basearch: The base architecture of the system, such as x86_64, i386, or arm.
$releasever: The release version of the operating system, such as 7, 8, or 9.
$arch: The exact architecture of the system, such as x86_64, i686, or armv7hl.
$uuid: A unique identifier for the system, generated by the product-id plugin.
$YUM0-$YUM9: Custom variables that can be set by the user in the /etc/yum/vars/ directory or the /etc/yum.conf file.
The other options are false or irrelevant. There is no yum confupdate command or yumd service, and changes to the yum configuration become active immediately after saving the files. The /etc/yum.conf file is not ignored if the /etc/yum.repos.d/ directory contains files, but the repository options in the /etc/yum.conf file can be overridden by the options in the .repo files. References:
Linux Essentials - Linux Professional Institute Certification Programs1
Exam 101 Objectives - Linux Professional Institute2
How to Use Yum Variables to Enhance your Yum Experience - Red Hat …3
Yum Variables - CentOS4
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