rpmbuild-md5: 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

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/rpmbuild-md5 - from package: fedora-packager

You may install the required package with command yum install {package}
Error in other languages:
rpmbuild-md5: bevel nie gevind nie
rpmbuild-md5: comandă negăsită
rpmbuild-md5: comando não encontrado
rpmbuild-md5: commande introuvable
rpmbuild-md5: command not found
rpmbuild-md5: käsku ei ole
rpmbuild-md5: không tìm thấy lệnh
rpmbuild-md5: komanda nerasta
rpmbuild-md5: Kommando nicht gefunden.
rpmbuild-md5: kommandot finns inte
rpmbuild-md5: komut yok
rpmbuild-md5: nie znaleziono polecenia
rpmbuild-md5: níor aimsíodh an t-ordú
rpmbuild-md5: no se encontró la orden
rpmbuild-md5: no s'ha trobat l'ordre
rpmbuild-md5: opdracht niet gevonden
rpmbuild-md5: parancs nem található
rpmbuild-md5: perintah tidak ditemukan
rpmbuild-md5: príkaz nenájdený
rpmbuild-md5: příkaz nenalezen
rpmbuild-md5: команда не найдена
rpmbuild-md5: командата не е открита
rpmbuild-md5: 命令找不到
rpmbuild-md5: コマンドが見つかりません