fbxkb: command not found

Have You tried accessing the binary with the full path?

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/fbxkb - from package: fbxkb

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