rawtoppm: 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/rawtoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/rawtoppm - from package: netpbm

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

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