xtalk: 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/xtalk - from package: xtalk

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

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