kon: 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/kon - from package: kon2

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