kdt2kdt: 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/kdt2kdt - from package: gerris-mpi
/usr/bin/kdt2kdt - from package: gerris

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

Error in other languages:
kdt2kdt: bevel nie gevind nie
kdt2kdt: comandă negăsită
kdt2kdt: comando não encontrado
kdt2kdt: commande introuvable
kdt2kdt: command not found
kdt2kdt: käsku ei ole
kdt2kdt: không tìm thấy lệnh
kdt2kdt: komanda nerasta
kdt2kdt: Kommando nicht gefunden.
kdt2kdt: kommandot finns inte
kdt2kdt: komut yok
kdt2kdt: nie znaleziono polecenia
kdt2kdt: níor aimsíodh an t-ordú
kdt2kdt: no se encontró la orden
kdt2kdt: no s'ha trobat l'ordre
kdt2kdt: opdracht niet gevonden
kdt2kdt: parancs nem található
kdt2kdt: perintah tidak ditemukan
kdt2kdt: príkaz nenájdený
kdt2kdt: příkaz nenalezen
kdt2kdt: команда не найдена
kdt2kdt: командата не е открита
kdt2kdt: 命令找不到
kdt2kdt: コマンドが見つかりません