xdot: 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/xdot - from package: xdot

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

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