xenwatchdogd: 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/lib/xen-4.4/bin/xenwatchdogd - from package: xen-utils-4.4

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

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