weka: 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/weka - from package: weka

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

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