How to fix locale: Cannot set LC_ALL to default locale: No such file or directory in APT

Export LC_ALL to the C locale, which is always available:

export LC_ALL=C
export LANG=C

This allows operations to proceed. To make it permanent for your user, add these lines to ~/.bashrc or ~/.profile.

First, ensure the locales package is installed:

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

Then generate the en_US.UTF-8 locale:

sudo locale-gen en_US.UTF-8

Update your system locale settings:

sudo update-locale LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8

Verify the locale was generated:

locale -a | grep en_US

Use the interactive locale configuration tool:

sudo dpkg-reconfigure locales

In the menu:
1. Check the box next to en_US.UTF-8 (or your preferred locale)
2. Press Space to select, Tab to navigate
3. Select the locale as your default when prompted
4. Press Enter to apply

For servers, choosing "None" as default is often recommended to avoid locale mismatches with remote clients.

Add these lines to your Dockerfile to prevent locale issues:

# Install locale support
RUN apt-get update && apt-get install -y locales && \
    locale-gen en_US.UTF-8 && \
    update-locale LANG=en_US.UTF-8

# Set environment variables
ENV LANG=en_US.UTF-8
ENV LC_ALL=en_US.UTF-8
ENV LC_CTYPE=en_US.UTF-8

Or for minimal images, just set LC_ALL to C:

ENV LC_ALL=C
ENV LANG=C

After applying fixes, verify your locale settings:

locale

You should see output without warnings. If you still see locale-related warnings, check that your SSH client isn't sending locale variables:

# On the remote system, check what LC_ALL is set to
echo $LC_ALL
echo $LANG

If they're empty or set to C, locale is correctly configured.