dncopy: 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/dncopy - from package: dnet-progs

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

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