task0: 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/task0 - from package: pvm-examples

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

Error in other languages:
task0: bevel nie gevind nie
task0: comandă negăsită
task0: comando não encontrado
task0: commande introuvable
task0: command not found
task0: käsku ei ole
task0: không tìm thấy lệnh
task0: komanda nerasta
task0: Kommando nicht gefunden.
task0: kommandot finns inte
task0: komut yok
task0: nie znaleziono polecenia
task0: níor aimsíodh an t-ordú
task0: no se encontró la orden
task0: no s'ha trobat l'ordre
task0: opdracht niet gevonden
task0: parancs nem található
task0: perintah tidak ditemukan
task0: príkaz nenájdený
task0: příkaz nenalezen
task0: команда не найдена
task0: командата не е открита
task0: 命令找不到
task0: コマンドが見つかりません