xyscan: 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/xyscan - from package: xyscan

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

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