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Well I've been around computers since the late 80's(I was like 3 actually). Went the whole mile: Atari Xl-XE, MS-DOS, Windows 3.1, 95, etc. Then started using Linux because of the looks(yes I know, Compiz-Fusion was the real reason to explore Linux) and now is installed in all my machines. I've even have it in Windows 10.

I've assembled machines from scratch before and you could always boot to "MS-DOS", that is what I remember and that made me wonder.

How was Unix installed back in the 80's or late 70's(I wasn't even alive)? Was it trivial like boot a big floppy or black magic involved?

It happens that I can't find any references to it and people in my country just don't get Free Software thing.

EDIT:

I've skipped a crucial part, I feel dumb because I didn't think about that in the first place.

Eveything starts with the boot sequence, which isn't an Operating System, but it's in ROM memory, like the BIOS(In my mind is a very minimalistic OS for machine config) and other stuff, like the boot sequence. At this stage it will look for the devices listed in the BIOS then it will iterate them in order, till one device responds with the boot instructions, like the ones in the tapes. So no initial OS is necesary and Unix can be installed.

Dumb mistakes, takes you the long way, but surely you learn more.

  • Neardupe unix.stackexchange.com/questions/442323/… which links to retrocomputing.SX which is probably better for this. – dave_thompson_085 May 30 '18 at 5:58
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    They installed it from tapes. Perhaps you know the wrong people, I thought South America was keen on the open source movement. upload.wikimedia.org/wikipedia/commons/thumb/8/8f/… – Rui F Ribeiro May 30 '18 at 7:36
  • Unix isn't and never was "Free Software". SCO Xenix which was the first serious Unix-like system for intel hardware cost serious money. That was installed with floppies. On "real" hardware the installation was done with tape. – wurtel May 30 '18 at 7:44
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    We do include questions on history here, as long as they are questions specifically about Unix and Linux history, which I would argue How did people install it? is. However, this is not a narrow question to answer. There was, after all, a range of machines upon which one could install Unices. – JdeBP May 30 '18 at 8:16
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    In the 1970s on a PDP-11, you just booted from a dec-tape to install – schily May 30 '18 at 9:30
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I think you are asking how the initial installation of Unix was performed. Many computers in that era were designed to run Unix, and came with the operating system pre-installed on the hard disk or on floppies. Installing was just a question of providing a disk with the proper contents.

But you might be asking, by what means does the system install the operating system in memory when it starts up?

Here is an example. The AT&T 3B1 aka "Unix PC" had a ROM that contained a bootstrap program, at addresses 800000-BFFFFF. When the system is reset, its Motoroloa 68010 CPU loads the stack pointer from 000000-2, loads the program counter from 000004-6 and jumps. During a reset the hardware forces address bit 23 high, effectively mapping the ROM to main memory, so the system is really running the program in ROM. That program in ROM initializes the different hardware components, runs some diagnostics, and crucially loads the operating system from floppy or disk by loading and running a bootblock. The code in the bootblock would load the kernel and start executing init, in the same was the a modern system does.

(More info in the manuals, see mirror by Philip Pemberton AT&T 3B1 Emulator)

You could theoretically use this knowledge to install something other that Unix on such as machine. But there wasn't always a hardware abstraction layer like the BIOS on a PC, so the program that was booted had to be more tightly coupled to the hardware.

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