dvbnet: command not found

Have You tried accessing the binary with the full path?

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/dvbnet - from package: dvb-apps

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