vtund: 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/sbin/vtund - from package: vtun

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

On Debian possible default full paths are:

/usr/sbin/vtund - from package: vtun

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

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