dkopp: 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/dkopp - from package: dkopp

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

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