hello.pvm: 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/hello.pvm - from package: pvm-examples

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

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