fatback: 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/fatback - from package: cernlib-packlib

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

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