amadmin: 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/amadmin - from package: amanda-server

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

On Debian possible default full paths are:

/usr/sbin/amadmin - from package: amanda-server

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

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