E: Unable to locate package ifconfig

This error message occurs when the package "ifconfig" is not found in the repository of your Linux distribution.

In recent versions of Ubuntu, ifconfig is not installed by default. Instead, you can use the "ip" command to perform similar network configuration tasks.

To install "ifconfig" on Ubuntu, you can try running the following command:

sudo apt-get update
sudo apt-get install net-tools

This should install the net-tools package, which includes ifconfig.