[talk] dmesg writes, usb stick booting
jpb at jimby.name
Sat Oct 7 16:51:16 EDT 2017
* Isaac (.ike) Levy <ike at blackskyresearch.net> [2017-10-05 20:05]:
> Hi All,
> I'm interested in doing some laptop hardware evaluations.
> I remember some years ago, somebody had made a cool multi-bsd bootable
> image, which had a writable partition which mounted under each BSD on
> it? (Was this Dru Lavigne if I remember correctly?)
> Did anyone keep that up? (I somehow remember it being a script which
> allowed a user to specify the disk image for each OS being loaded, so it
> was easier to keep up with OS updates.)
> Anyhow, if nobody remembers that gem - I'm totally looking for any easy
> instructions on making *BSD from USB media, with a writable partition
> (to simply get dmesg output). FreeBSD/OpenBSD are my particular
> targets, but any general instructions would be most appreciated.
For USB booting, you can download a TrueOS .img and write it directly to
a raw USB device. The current stable repo is at:
http://download.trueos.org/master/amd64/ and includes md5 and sha256 sums.
It's not multi-BSD, but it will allow you to boot to the install program,
where you can open a terminal window and run dmesg. That might get you
close to what you want.
In fact, if you install TrueOS as the "PersonaCrypt" version, you end
up with a bootable USB that boots directly into a usable system, and
(best part) leaves no traces behind when you are done. That's
probably the closest to your original ask.
The BSDCG study DVDs were on optical media with an EL Torito boot loader.
A script on the .iso boot block allowed you do boot any of the four
DVDs. Creating those DVDs is outlined (at a high level) here:
A third option is to modify the OpenBSD installation script and add
code to run dmesg (or do something else). I outlined how I did that
for a disk wiping setup using OpenBSD and TFTP. See:
http://jimby.name:81/obsd/obsd_wiper.pdf for details on the scripts
and how to rebuild the OpenBSD image. That use case is for disk wiping
not for dmesg, but you might be able to use the techniques there.
Just before emailing this note I found these via the Big G:
Layered on top of all this is the fact that most of the time, you still
have to modify the BIOS boot order to boot from USB. It may or may not
be bootable before the hard disk.
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