proxytunnel: 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/proxytunnel - from package: proxytunnel

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