An error occurred when trying to enter mongo shell.

$ mongo myDb
Failed global initialization: BadValue Invalid or no user locale set. Please ensure LANG and/or LC_* environment variables are set correctly.

For now, you can connect to mongo shell by using the default locale.

$ export LC_ALL=C

Also, according to the article below, uninstalling unnecessary mongo packages should resolve the issue.

[MongoDB] Notes when changing from mongo 2.6.5 to 2.6.4 because too many errors occurred on CentOS6.4 - Qiita

Reference Information

• What does export LANG=C mean | Redhat Enterprise Linux 4
• LANG=C doesn't output messages in English (I think) - Welcome to Hatena

That’s all from the Gemba.