rpmdumpheader: 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/rpmdumpheader - from package: deltarpm

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

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