gfan_groebnerfan: 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/gfan_groebnerfan - from package: gfan

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

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