aoe-discover: 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/sbin/aoe-discover - from package: aoetools

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

On Debian possible default full paths are:

/sbin/aoe-discover - from package: aoetools

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

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