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Re: Installer: 32 vs. 64 bit




On Fri, Oct 26, 2018 at 08:17:11PM +0100, Ben Hutchings wrote:
> On Fri, 2018-10-26 at 14:41 +0200, Juliusz Chroboczek wrote:
> > I've been encouraging my students to install Debian on their personal
> > machines, and we've found out that a lot of them get the wrong Debian
> > installer:
> > 
> >   - some of them attempt to install an AMD64 version of Debian in
> >     a 32-bit-only virtual machine;
> 
> Why are they creating 32-bit virtual machines?  Perhaps this is a bad
> default in the VM manaager?

Or an user error.  In either case, I don't get what a 32-bit _x86_ virtual
machine would be good for.  Are you teaching some code archeology?  Do you
want to prepare 32-bit images for something deeply embedded?  Neither sounds
an activity fit for your students.

For anything else, you want an amd64 kernel, possibly running i386 or x32
code.  Heck, even an i386 kernel would run fine on a 64-bit capable VM.

> >   - others attempt to install an i386 version on 64-bit hardware.
> 
> This should work, in general.  It won't work on a 64-bit system that
> only supports EFI boot - and the installer won't be able to report
> that, unless it includes a dummy 64-bit EFI program just to do that.

Installing i386 is also an user error unless you know you specifically need
that.  It's less egregious than a 32-bit VM, but still should be strongly
discouraged.  It kind of worked before, but then we got melted spectrum
mitigations -- new CPUs get a lot more to mitigate, and that really sucks on
32-bit kernels on 64-bit hardware.  Just don't.

i386 kernels should be used only if you actually have 32-bit hardware or
help someone who does.  You may still run 32-bit userland if you so wish.


Meow!
-- 
⢀⣴⠾⠻⢶⣦⠀ 
⣾⠁⢰⠒⠀⣿⡁ 10 people enter a bar: 1 who understands binary,
⢿⡄⠘⠷⠚⠋⠀ 1 who doesn't, D who prefer to write it as hex,
⠈⠳⣄⠀⠀⠀⠀ and 1 who narrowly avoided an off-by-one error.