guilt-refresh: 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/guilt-refresh - from package: guilt

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

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