hncdump: 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/hncdump - from package: hdf

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

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