niceload: 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/niceload - from package: parallel

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

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