hdfpack: 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/hdfpack - from package: hdf

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

On Debian possible default full paths are:

/usr/bin/hdfpack - from package: hdf4-tools

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

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