pnmtojpeg: 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 CentOS possible default full paths are:

/usr/bin/pnmtojpeg - from package: netpbm-progs

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/pnmtojpeg - from package: netpbm

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

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