Booting multiple BSDs.

Polytropon freebsd at
Sat Nov 14 10:30:35 UTC 2020

On Fri, 13 Nov 2020 19:02:29 -0800, David Christensen wrote:
> I am confident that there are several boot managers, likely one for each 
> of those four OS's, that can find multiple bootable OS drives/ slices/ 
> partitions and allow you to boot the OS of your choice.

First of all, it's important to understand the different stages
of OS booting, as well as the previous stage, likely involving
UEFI. In order to select (!) from multiple operating systems,
certain things must be neatly prepared or nothing will work
as intended.

There is a nice write-up by Manish Jain that deals with multi-
booting FreeBSD, Linux, and "Windows", but in case you do not
want a "Windows", leave out the corresponding parts - it will
work in a similar way with multiple BSDs or Linusi, Linuxens,
or Linuxera. ;-)

Document here:

In case you do _not_ have UEFI (i. e., you're using BIOS-based
systems), tools like Grub2 can be really helpful as boot manager.
It's easy to configure.

> But, my 
> experience is that keeping them all running is an exercise in "infinite 
> bug propagation"

"Get the worst out of all worlds!" :-)

It doesn't matter if you have a multi-OS setting based on
bare metal or in VMs - each OS you run will require a certain
amount of attention if you want to actually _use_ it for a
specific purpose instead of just "booting it".

> I would remove three of those drives and run one OS at a time.

In ye olden times, when BIOS was the thing in PC world, some
BIOS vendors had a drive management option integrated: You
could simply logically switch off drives, so they were still
powered on, but not detected anymore, so the only drive (and
maybe the data exchange drive) active were recognized, and
the OS was thinking it was the only one available. Go to BIOS,
switch off disk 1, switch on disk 2, and reboot - a totally
different OS boots, with no possibility to interfere (!) or
to "repair" (!!!) other system's disk content.

Today, you have PF12 boot selection. :-)

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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