rpm: 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:

/bin/rpm - from package: rpm

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

On Debian possible default full paths are:

/usr/bin/rpm - from package: rpm

You may install the required package with command apt-get install {package}

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