guilt-add: 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-add - from package: guilt

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

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