The "Failed to set locale, defaulting to C" warning message can occur when you try to run the yum command on a CentOS Linux system and the system is unable to set the correct locale.
The locale is a system setting that determines the language and cultural conventions used by the system, such as the character encoding, the date and time format, and the number and currency formats.
The "Failed to set locale" warning can occur if the system is unable to determine the correct locale settings or if the locale settings are invalid. This can happen if the /etc/locale.conf file is missing or if the LANG or LC_ALL environment variables are not set correctly.
To fix this issue, you can try setting the correct locale settings in the /etc/locale.conf file. For example, to set the locale to "en_US.UTF-8", you can add the following lines to the file:
LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8
You may also need to generate the necessary locale data by running the localedef command. For example, to generate the "en_US.UTF-8" locale, you can use the following command:
localedef -f UTF-8 -i en_US en_US.UTF-8
After making any changes to the locale settings, you will need to log out and log back in for the changes to take effect.
If you continue to have issues with the locale settings, you may want to check the system logs for more information about the cause of the issue. You may also want to consult the documentation for the locale command or seek additional help from a qualified system administrator or support representative.