rpmreaper: 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/rpmreaper - from package: rpmreaper

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

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