xl2tpd-control: 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/xl2tpd-control - from package: xl2tpd

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

On Debian possible default full paths are:

/usr/sbin/xl2tpd-control - from package: xl2tpd

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

Error in other languages:
xl2tpd-control: bevel nie gevind nie
xl2tpd-control: comandă negăsită
xl2tpd-control: comando não encontrado
xl2tpd-control: commande introuvable
xl2tpd-control: command not found
xl2tpd-control: käsku ei ole
xl2tpd-control: không tìm thấy lệnh
xl2tpd-control: komanda nerasta
xl2tpd-control: Kommando nicht gefunden.
xl2tpd-control: kommandot finns inte
xl2tpd-control: komut yok
xl2tpd-control: nie znaleziono polecenia
xl2tpd-control: níor aimsíodh an t-ordú
xl2tpd-control: no se encontró la orden
xl2tpd-control: no s'ha trobat l'ordre
xl2tpd-control: opdracht niet gevonden
xl2tpd-control: parancs nem található
xl2tpd-control: perintah tidak ditemukan
xl2tpd-control: príkaz nenájdený
xl2tpd-control: příkaz nenalezen
xl2tpd-control: команда не найдена
xl2tpd-control: командата не е открита
xl2tpd-control: 命令找不到
xl2tpd-control: コマンドが見つかりません