A few months ago, I attended an Oracle Cloud Infrastructure workshop in Oracle Reston. In one of the hands-on labs, it appears that the oci executable was not found in my compute instance:

To remedy this, simply run this command:

bash -c "$(curl -L https://raw.githubusercontent.com/oracle/oci-cli/master/scripts/install/install.sh)"

This is the output of the command above:

Now you are good to go: