r8tohdf: 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/r8tohdf - from package: hdf

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

On Debian possible default full paths are:

/usr/bin/r8tohdf - from package: hdf4-tools

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

Error in other languages:
r8tohdf: bevel nie gevind nie
r8tohdf: comandă negăsită
r8tohdf: comando não encontrado
r8tohdf: commande introuvable
r8tohdf: command not found
r8tohdf: käsku ei ole
r8tohdf: không tìm thấy lệnh
r8tohdf: komanda nerasta
r8tohdf: Kommando nicht gefunden.
r8tohdf: kommandot finns inte
r8tohdf: komut yok
r8tohdf: nie znaleziono polecenia
r8tohdf: níor aimsíodh an t-ordú
r8tohdf: no se encontró la orden
r8tohdf: no s'ha trobat l'ordre
r8tohdf: opdracht niet gevonden
r8tohdf: parancs nem található
r8tohdf: perintah tidak ditemukan
r8tohdf: príkaz nenájdený
r8tohdf: příkaz nenalezen
r8tohdf: команда не найдена
r8tohdf: командата не е открита
r8tohdf: 命令找不到
r8tohdf: コマンドが見つかりません