sdfget: 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/sdfget - from package: sdf

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