rapper: 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/rapper - from package: raptor

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

On Debian possible default full paths are:

/usr/bin/rapper - from package: raptor2-utils
/usr/bin/rapper - from package: raptor-utils

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

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