gpbs: 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/gpbs - from package: gnustep-back

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

On Debian possible default full paths are:

/usr/bin/gpbs - from package: gnustep-back-common

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

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