pnmcat: 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/pnmcat - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pnmcat - from package: netpbm

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

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