rpmpeek: 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/rpmpeek - from package: rpmdevtools

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

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