kadu: 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/kadu - from package: kadu

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

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