repo-rss: 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/repo-rss - from package: yum-utils

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

On Debian possible default full paths are:

/usr/bin/repo-rss - from package: yum-utils

You may install the required package with command apt-get install {package}

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