pnmsmooth: 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/pnmsmooth - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pnmsmooth - from package: netpbm

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

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