pcxtoppm: 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/pcxtoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pcxtoppm - from package: netpbm

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

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