debian all-in-one CD images (isos)

Debian used to be distributed on series of media.  In the 90s you may have had  however many CDs, and when you installed a package, the system asked you to insert a particular CD.  More recently, the official set of 3 DVDs seemed to cover most installations well, with further software probably coming over the network.  The common case of internet-connected hosts meant that a single small CD (in the original sense of the 650MB discs) did fine for bootstrapping to something that can install from the network.

Meanwhile, demand for CD (in the more general sense of mainstream 12cm optical media) images for debian appears to have put enough demand on debian infrastructure that debian came up with mitigations for the bandwidth load.  They made Jigdo, which is a shitmanteau involving jigsaw, and allows some bittorrent-esque downloading of ranges from different places.  They discouraged people downloading even full DVDs.  And, sadly, they seem to have avoided Bluray images altogether.

A full Debian image, containing all packages, has been of the order of tens of GB for some time.  The image I've just built for debian 11 is 55GB.  I remember debian 10 was 53GB.  From memory, I think debian 9 was also 53GB.

For several years, we've had Bluray / BD discs and burners with a capacity of 100GB.  This means that for the first time, a full Debian installer with all packages can exist on a single commonly-available read-only medium.

Cheap USB sticks exceeding 53GB in capacity have been around for longer.  And many bootable CD images live a double life as bootable hard-drive images, meaning you can use the same "ISO" image for the same purpose, as an installer, both on optical media and on a drive like a USB stick (I have yet to confirm whether my images built using the "debian-cd" software behave like this, or whether some other magic has to be added).

For the internet-connected case, none of this will be all that interesting.  But there are as many cases as ever for disconnected installation / normal operation of computers.  It doesn't have to be a Bitcoin signing-station, though it can be.  Could be: package install works normally on the plane, or wherever.  A workspace for really focussed work may feature computers with no internet, just to minimise distractions.  Perhaps guaranteed repeatability is important, meaning a policy of no external dependencies.  There is no shortage of use-cases for installations and package-installs to work well on disconnected hosts.

The milestone of optical media capacity exceeding the size of a debian release appears to have passed the debian folk by.

The conditions that led to jigdo, and discouraging full images, no longer apply.  Put simply, bandwidth is much cheaper, and debian didn't get much bigger.  A 10 Gbps port costs only 1200 GBP per month.  Starting from here, as opposed to starting from 15 years ago, it would make sense to allocate resources to saving bandwidth only when several of those are saturated.  For net installs, you still want a tiny image to get started, but there is no reason not to have the full images available too.

more to come later on the debian tools to build these images, which are rather shonky, and my own publication of the images I built.


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