nfdump: 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/bin/nfdump - from package: nfdump

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

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