gfan_topolyhedralfan: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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_topolyhedralfan - from package: gfan

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