Para garantizar que un sistema se actualice, lo mejor es estar informado de las actualizaciones disponibles. Apticron es un programa que se ejecuta diariamente de forma automática, y comprueba si hay actualizaciones disponibles para nuestro sistema, y luego informa al administrador del sistema por e-mail.

root@server:~# apt install apticron

Ne el archivo/etc/apticron/apticron.conf se puede configurar la dirección de correo para notificación de las actualizaciones:

# apticron.conf
#
# set EMAIL to a space separated list of addresses which will be notified of
# impending updates
#
EMAIL="root"

#[...]

Siempre que haya una actualización disponible para el sistema, se enviará un e-mail al administrador del sistema:

Subject: 1 Debian package update(s) for server.home.lan
To: <root@server.home.lan>
Date: Thu,  6 Jul 2017 01:52:05 +0100 (WEST)
From: root@server.home.lan (root)

apticron report [Thu, 06 Jul 2017 01:52:05 +0100]
========================================================================

apticron has detected that some packages need upgrading on:

	server.home.lan 
	[ 192.168.1.100 ]

The following packages are currently pending an upgrade:

	libtiff5 4.0.8-2+deb9u1

========================================================================

Package Details:

apt-listchanges: Reading changelogs...
apt-listchanges: Changelogs
---------------------------

--- Changes for tiff (libtiff5) ---
tiff (4.0.8-2+deb9u1) buster-security; urgency=high

  * Backport security fixes:
    - CVE-2017-9936, memory leak in error code path of JBIGDecode()
      (closes: #866113),
    - prevent out of memory in gtTileContig() on corrupted files,
    - CVE-2017-10688, assertion failure in TIFFWriteDirectoryTagCheckedXXXX()
      (closes: #866611).
  * Add required _TIFFReadEncodedStripAndAllocBuffer@LIBTIFF_4.0 symbol to the
    libtiff5 package.

 -- Laszlo Boszormenyi (GCS) <gcs@debian.org>  Sun, 02 Jul 2017 08:36:06 +0000

========================================================================

You can perform the upgrade by issuing the command:

	apt-get dist-upgrade

as root on server.home.lan

--
apticron

Entonces, el administrador podrá actualizar el sistema con el comando 'apt full-upgrade o apt-get dist-upgrade''.

• 5.2.1 Servidor SMTP