-bash: yum: command not found

This error message means that the command "yum" is not recognized by the system. "yum" is a package manager used on some Linux distributions, such as CentOS and Red Hat Enterprise Linux.

If you are using a different Linux distribution, it may have a different package manager installed by default. For example, Debian and Ubuntu use "apt-get" and "apt" as their package managers.

If you are using CentOS or Red Hat Enterprise Linux, you may need to install the "yum" package manager. To do so, you can run the following command as the root user:

sudo dnf install yum

Alternatively, you can use the "dnf" package manager instead of "yum". "dnf" is the default package manager on newer versions of CentOS and Red Hat Enterprise Linux.