aoe-revalidate: 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-revalidate - from package: aoetools

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

On Debian possible default full paths are:

/sbin/aoe-revalidate - from package: aoetools

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

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