xxkb: 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/xxkb - from package: xxkb

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

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