rpmdev-vercmp: 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/rpmdev-vercmp - from package: rpmdevtools

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

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