burnK6: 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/burnK6 - from package: cpuburn

You may install the required package with command apt-get install {package}
Error in other languages:
burnK6: bevel nie gevind nie
burnK6: comandă negăsită
burnK6: comando não encontrado
burnK6: commande introuvable
burnK6: command not found
burnK6: käsku ei ole
burnK6: không tìm thấy lệnh
burnK6: komanda nerasta
burnK6: Kommando nicht gefunden.
burnK6: kommandot finns inte
burnK6: komut yok
burnK6: nie znaleziono polecenia
burnK6: níor aimsíodh an t-ordú
burnK6: no se encontró la orden
burnK6: no s'ha trobat l'ordre
burnK6: opdracht niet gevonden
burnK6: parancs nem található
burnK6: perintah tidak ditemukan
burnK6: príkaz nenájdený
burnK6: příkaz nenalezen
burnK6: команда не найдена
burnK6: командата не е открита
burnK6: 命令找不到
burnK6: コマンドが見つかりません