default behaviour for unattended-upgrades

Since we had used Ubuntu 24.04 minimal images for some new servers, we had to check if unattended upgrades were installed and enabled -

https://askubuntu.com/questions/916722/how-to-verify-that-unattended-upgrades-are-enabled

Basically we have to check if an auto-upgrades file is present in /etc/apt/apt.conf.d/ and check if the Allowed-Origins are appropriate. In the case of this Ubuntu 24.04 minimal Azure image, the allowed origins not commented out were:

       "${distro_id}:${distro_codename}";

        "${distro_id}:${distro_codename}-security";

        // Extended Security Maintenance; doesn't necessarily exist for

        // every release and this system may not have it installed, but if

        // available, the policy for updates is such that unattended-upgrades

        // should also install from here by default.

        "${distro_id}ESMApps:${distro_codename}-apps-security";

        "${distro_id}ESM:${distro_codename}-infra-security";

So, all is good.