gngb: 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 Debian possible default full paths are:

/usr/bin/gngb - from package: gngb

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

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