sdnm: 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/sdnm - from package: sdcc

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

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