When provisioning servers or writing automation scripts, manually running dpkg-reconfigure locales becomes impractical. The interactive selection process breaks automation flows and complicates deployment pipelines. Here's a bulletproof method to handle this programmatically.

First, ensure locales package is installed:

sudo apt-get update && sudo apt-get install -y locales

Create a minimal locale configuration file (replace contents of /etc/locale.gen):

echo "en_US.UTF-8 UTF-8" | sudo tee /etc/locale.gen
sudo locale-gen

Update the default locale configuration:

echo "LANG=en_US.UTF-8" | sudo tee /etc/default/locale
sudo update-locale LANG=en_US.UTF-8

To confirm the changes took effect:

# Check current locale
locale

# Verify /etc/default/locale contents
grep -E '^LANG=' /etc/default/locale

# Alternative verification
localectl status

For Docker containers or minimal installations where locale-gen isn't available:

sudo apt-get install -y language-pack-en
sudo update-locale LANG=en_US.UTF-8
source /etc/default/locale

A complete implementation with error handling:

#!/bin/bash

set -e

# Install prerequisites
apt-get update && apt-get install -y locales

# Configure locale
echo "en_US.UTF-8 UTF-8" > /etc/locale.gen
locale-gen en_US.UTF-8
update-locale LANG=en_US.UTF-8

# Verification
if ! grep -q "LANG=en_US.UTF-8" /etc/default/locale; then
    echo "Locale configuration failed!" >&2
    exit 1
fi

echo "Locale configured successfully"

• If changes don't reflect, try logging out and back in or rebooting
• For SSH sessions, ensure AcceptEnv LANG LC_* is set in sshd_config
• Check existing environment variables with env | grep -E 'LC_|LANG'

When automating server deployments or container builds, interactive commands like dpkg-reconfigure locales become problematic. We need a fully scriptable solution that:

• Installs required packages without prompts
• Configures en_US.UTF-8 as the exclusive locale
• Handles all configuration files properly

Here's the robust implementation I've tested across Debian/Ubuntu versions:

#!/bin/bash
# Install locales package non-interactively
DEBIAN_FRONTEND=noninteractive apt-get install -y locales

# Configure locales
echo "en_US.UTF-8 UTF-8" > /etc/locale.gen
locale-gen en_US.UTF-8

# Set system-wide default
update-locale LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8

# Clean up other locale settings
sed -i '/^[^#]/d' /etc/locale.gen

Add these checks to your script to validate the configuration:

# Verify locale generation
if ! locale -a | grep -q "en_US.utf8"; then
    echo "Locale generation failed" >&2
    exit 1
fi

# Check /etc/default/locale
if ! grep -q '^LANG=en_US.UTF-8$' /etc/default/locale || \
   [ $(grep -v '^#' /etc/default/locale | wc -l) -ne 1 ]; then
    echo "Locale configuration incomplete" >&2
    exit 1
fi

For container environments, this optimized version works best:

FROM debian:bullseye
RUN apt-get update && \
    DEBIAN_FRONTEND=noninteractive apt-get install -y locales && \
    echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && \
    locale-gen en_US.UTF-8 && \
    update-locale LANG=en_US.UTF-8 && \
    rm -rf /var/lib/apt/lists/*

ENV LANG=en_US.UTF-8 \
    LANGUAGE=en_US:en \
    LC_ALL=en_US.UTF-8

Missing locale-gen: Ensure the locales package is installed before running locale-gen

Partial configuration: The update-locale command sometimes doesn't update all files - manually verify /etc/environment if needed

Service restarts: Some services may need restarting after locale changes, particularly those running in init systems