rb-site: 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/rb-site - from package: ReviewBoard

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