How to fix dpkg: warning: PATH is not set in APT

When switching to the root user, always use the dash flag:

su -

Instead of just:

su

The dash flag ensures that the root user's full login environment is initialized, including the correct PATH variable containing /usr/sbin, /usr/bin, /sbin, and /bin.

Check if your PATH includes the necessary system directories:

echo $PATH

You should see output similar to:

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

If this is missing or incomplete, proceed to the next step.

If PATH is not set correctly, export the full path before running dpkg:

export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Then run your dpkg command:

dpkg -i package.deb

If you prefer not to use 'su -', you can use sudo with the -i flag:

sudo -i

This also loads the target user's login shell and sets up the environment correctly. You can then run dpkg commands without PATH issues.