How to fix dpkg: error: --add-architecture needs exactly one argument in APT

First, review the exact command you ran that produced the error. Look for any extra flags or arguments after the architecture name.

# Examples of INCORRECT syntax that cause this error:
dpkg --add-architecture i386 --root /     # Extra flag
dpkg --add-architecture i386 arm64        # Multiple architectures
dpkg --add-architecture "i386" extra      # Extra argument

The --add-architecture command takes exactly one argument: the architecture name. Remove any additional flags or arguments.

# Correct syntax:
sudo dpkg --add-architecture i386
sudo dpkg --add-architecture arm64
sudo dpkg --add-architecture armhf

Common valid architecture names:
- i386 - 32-bit x86
- amd64 - 64-bit x86 (usually the default)
- arm64 - 64-bit ARM
- armhf - 32-bit ARM with hardware floating point
- armel - 32-bit ARM with soft floating point
- ppc64el - 64-bit PowerPC (little-endian)

If you need to enable support for multiple foreign architectures, run dpkg --add-architecture once for each architecture:

sudo dpkg --add-architecture i386
sudo dpkg --add-architecture arm64
sudo apt-get update

Do not attempt to pass multiple architectures in one command.

After successfully adding the architecture, update your package lists so apt is aware of packages available for the new architecture:

sudo apt-get update

You can now install packages for that architecture using the syntax package:architecture. For example:

sudo apt-get install libc6:i386       # Install 32-bit libc6
sudo apt-get install wine:i386        # Install 32-bit Wine

Confirm that the architecture is now registered on your system:

# View your system's native architecture:
dpkg --print-architecture

# View all foreign architectures you've added:
dpkg --print-foreign-architectures

The architecture you added should appear in the output of the second command.