ppc-koji: 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
/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/ppc-koji - from package: fedora-packager

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