ptunnel: 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/sbin/ptunnel - from package: ptunnel

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

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