ddstool: 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/ddstool - from package: dds2tar

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

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