gfan_tropicalrank: 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_tropicalrank - from package: gfan

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

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