gfan_tropicalfunction: 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_tropicalfunction - from package: gfan

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

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