pnmnorm: 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/pnmnorm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pnmnorm - from package: netpbm

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

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