rpmusage: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

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

On CentOS possible default full paths are:

/usr/bin/rpmusage - from package: rpmorphan

You may install the required package with command yum install {package}

Error in other languages:
rpmusage: bevel nie gevind nie
rpmusage: comandă negăsită
rpmusage: comando não encontrado
rpmusage: commande introuvable
rpmusage: command not found
rpmusage: käsku ei ole
rpmusage: không tìm thấy lệnh
rpmusage: komanda nerasta
rpmusage: Kommando nicht gefunden.
rpmusage: kommandot finns inte
rpmusage: komut yok
rpmusage: nie znaleziono polecenia
rpmusage: níor aimsíodh an t-ordú
rpmusage: no se encontró la orden
rpmusage: no s'ha trobat l'ordre
rpmusage: opdracht niet gevonden
rpmusage: parancs nem található
rpmusage: perintah tidak ditemukan
rpmusage: príkaz nenájdený
rpmusage: příkaz nenalezen
rpmusage: команда не найдена
rpmusage: командата не е открита
rpmusage: 命令找不到
rpmusage: コマンドが見つかりません