pamsumm: 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/pamsumm - from package: netpbm-progs

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

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