cobbler-register: 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/cobbler-register - from package: koan

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

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