puf: 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/share/doc/mh-book/examples/mh/bin/puf - from package: mh-book
/usr/bin/puf - from package: puf

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

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