Debian 9.7 released today, I wanted to update my pendrive but as I go to the release page there are offline installers, links below
and
I am well aware of the primary difference but what bugs me was that a image in Debian current is about 3.4 - 4.4 GB, labeled as DVD 1 .. 2 .. 3, while max file size in current live is 2.4 GB, KDE. Why?
Debian Live is a self-contained live image, i.e. something you can boot from a DVD or USB media without actually installing it. It contains the most common applications, but not everything Debian has to offer. It can also be used to start an actual installation, but you can also use Debian Live as a stand-alone system rescue tool, for example.
The offline installation images contain the full content of the Debian package repositories for that specific release+architecture combination, arranged in popularity order. If you're installing Debian to a system that has internet connectivity, you'll most likely need only the first DVD: if you need something that is not on the first DVD, it will automatically be downloaded from the internet-based repositories.
The only reason to download the full set of DVDs would be a need to install Debian to a system that has no internet access at all, with a requirement to be able to install even the most obscure optional packages Debian has to offer.
The contents of the DVDs are quite different (beyond the live v. non-live side of things): the first DVD in the DVD images contains 4566 packages, whereas the KDE live image contains 2604.
The "Live" images are intended to be run standalone, no-installation-required.
From the Debian CD FAQ:
Is a Debian "live CD" available?
Yes. A so-called "live CD", or more precisely, a "live system", is a complete system prepared for a DVD, USB key or other medium. You do not need to install anything on the hard drive. Instead you boot from the medium (DVD or USB key) and are able to start working on the machine right away. All programs run directly from the medium.
The "current" images, on the other hand, are intended for installation to the internal HD. That means that they include far more optional packages, most of which you won't need to install.
From your "current" link:
There are lots of files here! Do I need all of them?
In most cases it is not necessary to download and use all of these images to be able to install Debian on your computer. Debian comes with a massive set of software packages, hence why it takes so many disks for a complete set. Most typical users only need a small subset of those software packages.
Initially, you will only need to download and use the first image of a set (labelled as debian-something-1) to be able to start the Debian installer and set up Debian on your computer.
You could use the live CD for a full installation -- you'd just be starting with a smaller set of pre-downloaded packages. See also Is it possible to install a Linux desktop environment from a live CD?.
If you want to
run a live-only system from your USB pendrive, it is obvious that you want to download the "Current - live" iso file, and you can clone from the iso file to the pendrive,
run a persistent live system from your USB pendrive, you can download the "Current - live" iso file and use mkusb to create a persistent live system with a partition for persistence, so that you can use the whole pendrive,
install Debian, make a full installation, you can either download the "Current" iso file(s) or the "Current - live" iso file. Both can be used to install Debian. You can clone from the iso file to the pendrive, boot from the pendrive and install Debian (usually into an internal drive).
The "Current" DVD iso files contain 'only' an installer, that you can clone to a USB pendrive;
There are also smaller versions of the "Current" iso files, for example the debian...netinst.iso files, that you can download, and there are several ways to download Debian. Find the best way for you depending on your internet connection and how many installations you intend to do.
See this link, www.debian.org/distrib
