Hi and welcome to LinuxQuestions!
Most likely you are trying these commands as a normal user, whereas they are system commands
reserved to the system administrator (that is the Linux super-user, named root
). As you can see they are in the /usr/sbin directory, that according to the Filesystem Hierarchy Standard
contains commands for which root's privileges are required.
Indeed, if you check your PATH environment variable:
you cannot see /sbin nor /usr/sbin in the (colon separated) list of directories, hence the command not found
error. On the contrary, if you gain root's privileges you will see them listed and you'll have these commands at your disposal.
In addition to the official Red Hat documentation, I suggest the more friendly "The Linux Command Line"
book, that explains these basic concepts in a plain and clear way.