[Solved]Can we use Debian's official mirrors instead of Linode's?

Nope, just change the URL

There's no reason to use Debian's mirrors, though. They're exactly the same.

Some mirrors might be hours older than others, of course, but AFAIK Linode has a good update frequency. And this post is hours old by now anyway.

Yeah you're right, I changed to:

deb  http://deb.debian.org/debian stretch main
deb-src  http://deb.debian.org/debian stretch main

And I have 0 updates.

But when I do:

cat /etc/debian_version

I still get 9.1.

Then I saw in the announcement:
> Due to an oversight while preparing the point release, the usual update to the "base-files" package to reflect the new version was unfortunately not included. An updated package will be made available via "stretch-updates" in the near future.

So it appears version number will remain 9.1 for now, even though the system is actually 9.2.

Thanks!

You should make sure you have stretch-updates in your sources.list, because that updated base-files package was released within hours of the 9.2 release. Your /etc/apt/sources.list should look something like this (assuming you use Linode for your mirror):

deb http://mirrors.linode.com/debian stretch main
deb http://mirrors.linode.com/debian stretch-updates main
deb http://security.debian.org/debian-security stretch/updates main

If you want the ability to download source packages too (most people won't care about this), duplicate those lines and replace the "deb" at the start with "deb-src". Additionally, you can add "contrib" and/or "non-free" to the end of the lines to get additional packages which aren't part of the main repository.