aggregate: 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/aggregate - from package: aggregate

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

On Debian possible default full paths are:

/usr/bin/aggregate - from package: aggregate

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

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