🌍 How to Fix Incorrect Locale Warnings on Linux

Are you getting locale-related warnings on your Linux system such as:

bash
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = "en_US:en",
LC_ALL = (unset),
LC_TIME = "uk_UA.UTF-8",
LC_MONETARY = "uk_UA.UTF-8",
LC_ADDRESS = "uk_UA.UTF-8",
LC_TELEPHONE = "uk_UA.UTF-8",
LC_NAME = "uk_UA.UTF-8",
LC_MEASUREMENT = "uk_UA.UTF-8",
LC_IDENTIFICATION = "uk_UA.UTF-8",
LC_NUMERIC = "uk_UA.UTF-8",
LC_PAPER = "uk_UA.UTF-8",
LANG = "en_US.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
apt-listchanges: Can't set locale; make sure $LC_* and $LANG are correct!

These warnings typically appear when the system is missing the required locale definitions. Here’s how to fix it.

✅ Solution: Reconfigure Locales

To generate and configure the appropriate locales on Debian-based systems (e.g., Ubuntu), run:

sudo dpkg-reconfigure locales

📝 Steps:

1. Select one or more locales (use space to mark), e.g., en_US.UTF-8 and/or uk_UA.UTF-8.
2. Choose the default locale when prompted.
3. Confirm and wait for the system to regenerate the locale files.

💡 Alternative: Manually Set Locales (Optional)

For Docker containers, CI/CD, or minimal systems, you can set locale variables manually:

export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8

To make this persistent, add the above lines to your shell profile (~/.bashrc, ~/.zshrc, or /etc/environment).