pvrg-jpeg: 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/pvrg-jpeg - from package: pvrg-jpeg

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

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