gfan_version: 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_version - from package: gfan

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

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