polygraph-udp2tcpd: 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/bin/polygraph-udp2tcpd - from package: polygraph

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

Error in other languages:
polygraph-udp2tcpd: bevel nie gevind nie
polygraph-udp2tcpd: comandă negăsită
polygraph-udp2tcpd: comando não encontrado
polygraph-udp2tcpd: commande introuvable
polygraph-udp2tcpd: command not found
polygraph-udp2tcpd: käsku ei ole
polygraph-udp2tcpd: không tìm thấy lệnh
polygraph-udp2tcpd: komanda nerasta
polygraph-udp2tcpd: Kommando nicht gefunden.
polygraph-udp2tcpd: kommandot finns inte
polygraph-udp2tcpd: komut yok
polygraph-udp2tcpd: nie znaleziono polecenia
polygraph-udp2tcpd: níor aimsíodh an t-ordú
polygraph-udp2tcpd: no se encontró la orden
polygraph-udp2tcpd: no s'ha trobat l'ordre
polygraph-udp2tcpd: opdracht niet gevonden
polygraph-udp2tcpd: parancs nem található
polygraph-udp2tcpd: perintah tidak ditemukan
polygraph-udp2tcpd: príkaz nenájdený
polygraph-udp2tcpd: příkaz nenalezen
polygraph-udp2tcpd: команда не найдена
polygraph-udp2tcpd: командата не е открита
polygraph-udp2tcpd: 命令找不到
polygraph-udp2tcpd: コマンドが見つかりません