hdftor8: 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/hdftor8 - from package: hdf

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

On Debian possible default full paths are:

/usr/bin/hdftor8 - from package: hdf4-tools

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

Error in other languages:
hdftor8: bevel nie gevind nie
hdftor8: comandă negăsită
hdftor8: comando não encontrado
hdftor8: commande introuvable
hdftor8: command not found
hdftor8: käsku ei ole
hdftor8: không tìm thấy lệnh
hdftor8: komanda nerasta
hdftor8: Kommando nicht gefunden.
hdftor8: kommandot finns inte
hdftor8: komut yok
hdftor8: nie znaleziono polecenia
hdftor8: níor aimsíodh an t-ordú
hdftor8: no se encontró la orden
hdftor8: no s'ha trobat l'ordre
hdftor8: opdracht niet gevonden
hdftor8: parancs nem található
hdftor8: perintah tidak ditemukan
hdftor8: príkaz nenájdený
hdftor8: příkaz nenalezen
hdftor8: команда не найдена
hdftor8: командата не е открита
hdftor8: 命令找不到
hdftor8: コマンドが見つかりません