vfu: 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
/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/vfu - from package: vfu

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