hdfview: 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/hdfview - from package: hdfview

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

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