asadmin: 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/asadmin - from package: python2-boto
/usr/bin/asadmin - from package: python-boto

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

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