iwpmd: command not found

Have You tried accessing the binary with the full path?

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/iwpmd - from package: libiwpm

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