gfan_minkowskisum: 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_minkowskisum - from package: gfan

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