duma: 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/duma - from package: duma

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

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