npcd: 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 CentOS possible default full paths are:

/usr/sbin/npcd - from package: pnp4nagios

You may install the required package with command yum install {package}

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