task1: 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/task1 - from package: pvm-examples

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

Error in other languages:
task1: bevel nie gevind nie
task1: comandă negăsită
task1: comando não encontrado
task1: commande introuvable
task1: command not found
task1: käsku ei ole
task1: không tìm thấy lệnh
task1: komanda nerasta
task1: Kommando nicht gefunden.
task1: kommandot finns inte
task1: komut yok
task1: nie znaleziono polecenia
task1: níor aimsíodh an t-ordú
task1: no se encontró la orden
task1: no s'ha trobat l'ordre
task1: opdracht niet gevonden
task1: parancs nem található
task1: perintah tidak ditemukan
task1: príkaz nenájdený
task1: příkaz nenalezen
task1: команда не найдена
task1: командата не е открита
task1: 命令找不到
task1: コマンドが見つかりません