update.php: 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 Debian possible default full paths are:

/usr/share/simplesamlphp/modules/aggregator2/bin/update.php - from package: simplesamlphp

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

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