dwdiff: 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/dwdiff - from package: dwdiff

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

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