kxc-add-key: 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/kxc-add-key - from package: kxc

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

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