wmrack: 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/wmrack - from package: wmrack

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

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