tunneler: 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 CentOS possible default full paths are:

/usr/bin/tunneler - from package: tunneler

You may install the required package with command yum install {package}

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