ncpus: 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/ncpus - from package: mdm

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

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