gouldtoppm: 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/gouldtoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/gouldtoppm - from package: netpbm

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

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