Failed to set locale, defaulting to C warning message on CentOS Linux when running yum

Whenever I run yum command, I get an error or warning that read as Failed to set locale, defaulting to C. How do I fix this issue on CentOS 7 Linux server? Why do I get “Failed to set locale, defaulting to C” when using yum on CentOS 6 or Fedora Linux system? How do I fix it?

Locales define language and country-specific setting for your programs and shell session. You can use locales to see the date, time, number, currency and other values formatted as per your country or language on a Linux or Unix-like system. To set system’s locale, you need use shell variable. For example, LANG variable can be used to set en_US (English US) language.

Understanding “Failed to set locale, defaulting to C” when using yum

It means local values did not correctly setup on your CentOS Linux server or desktop system. The following instructions should help you to fix this problem.

How do I find out current values for my language?

Just type the following command:
$ locale
# locale
Sample outputs:

Fig.01: How do I show current locale settings on a Linux or Unix?

How do I solve this problem?

To set i18n stuff CentOS/Fedora and RedHat Enterprise Linux call a special script called /etc/profile.d/ Make sure this file exist in your system:
$ ls -l /etc/profile.d/
If file exist just call it:
$ source /etc/profile.d/
Verify that LANG and LC_* shell variable are set:
$ echo "$LANG"
$ echo "$LC_CTYPE"

How to set my own LANG and LC_ALL/LC_CTYPE variables

You can set it manually in your own directory as follows:
$ vi ~/.bashrc
OR globally in /etc/profile.d/ for bash/sh/ksh shell:
$ sudo vi /etc/profile.d/
Append the following
## Indian English ##
export LANG=en_IN
export LANGUAGE=en_IN:en
export LC_CTYPE=en_IN.UTF-8

For US English:
## US English ##
export LANG=en_US.UTF-8
export LANGUAGE=en_US.UTF-8
export LC_CTYPE=en_US.UTF-8

Save and close the file. Log out and log in again. Or just call this file:
$ source /etc/profile.d/

How do I test it?

Now you can use yum command without any issues:
$ sudo yum update
$ sudo yum search nload
$ sudo install nload