software-properties-kde: 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/software-properties-kde - from package: software-properties-kde

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

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