lcg-aa: 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/lcg-aa - from package: lcg-util

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

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