ncgen-hdf: 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 Debian possible default full paths are:

/usr/bin/ncgen-hdf - from package: hdf4-tools

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

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