hackbench: 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/hackbench - from package: rt-tests

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

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