[UPDATE] New Boot-Loader Menu -- version 1.4

[Devin Teske]

> -----Original Message-----
> From: Lars Engels [mailto:lars.engels at 0x20.net]
> Sent: Monday, May 09, 2011 2:19 AM
> To: Devin Teske
> Cc: FreeBSD Hackers
> Subject: Re: [UPDATE] New Boot-Loader Menu -- version 1.4
> 
> On Thu, May 05, 2011 at 01:20:43AM -0700, Devin Teske wrote:
> > Hello fellow -hackers,
> >
> > I'm so very proud to offer the latest update to my new boot loader
> > menu -- version 1.4 -- addressing ACPI detection, bringing it in-line
> > with HEAD.
> >
> > It took some work and a few days, but I got it! Have a look below for
> > six different displays (three different scenarios -- i386 w/ ACPI,
> > i386 w/o ACPI, and non-i386 -- each in both B&W and Color).
> >
> 
> Hi Devin,
> 
> PC-BSD also has a slightly patched loader menu compared to the stock FreeBSD
> version.

Does PC-BSD have CVSweb that I can browse? Link?


> I.E. you can also set unset verbose mode and ACPI with it.
> Some days ago there was a proposal on a PC-BSD list to add an option to boot a
> different kernel if one is found in /boot.
> Would it be possible to addi this function to your boot menu?

No need. The basic constructs are there already, we just need to expand on them.

Here's how I've implemented a hard-coded list of kernels to choose from for our systems (to be implemented in /boot/menu.rc):

\ Set kernel paths (see menu_caption[2] below)
set kernel_prefix="/kernels/"
	\ NOTE: We like to keep our kernels in `/kernels'
set kernel[0]="FIS-i386-8.1p1"
set kernel[1]="GENERIC-i386-8.1p1"
set kernel_suffix=".kgz"
	\ NOTE: This is on our CD/DVD, so kernels are kgzip(8)'d

\ Set default boot kernel
set kernel="${kernel_prefix}${kernel[0]}${kernel_suffix}"

\ Initialize main menu constructs (variables are read by `menu.4th')

set menu_caption[1]="Boot [ENTER]"
set menu_command[1]="boot"

set menu_caption[2][0]="Kernel: ${kernel[0]} (1of2)"
set menu_caption[2][1]="Kernel: ${kernel[1]} (2of2)"
set menu_caption[2]="${menu_caption[2][0]}"
set menu_command[2]="cycle_kernel"

\ ... rest of menu ...

The magic is the "cycle_kernel" command (see `/boot/menu.4th'). The `cycle_kernel' command is a wrapper to the `cycle_menuitem' command (similar to how `toggle_verbose', `toggle_acpi', and `toggle_singleuser' are wrappers to the `toggle_menuitem' command). Like the `toggle_menuitem' command, the `cycle_menuitem' command uses a system of internal state variables to track which menuitem text is to be displayed for that individual menuitem. Whereas the `toggle_menuitem' command automatically toggles the text of a menuitem between the `menu_caption[x]' and `toggled_text[x]' variables, the `cycle_menuitem' command automatically cycles through the `menu_caption[x][y]' variables, cycling back to y=0 when it gets to an undefined `y' value.

However, hard-coding an alternate kernel choice is something that I wouldn't condone for an actual release. Instead, what I would recommend is to dynamically allocate the kernel menu if/when multiple kernels are discovered/configured. That's something that is currently not coded (dynamic detection of kernels in /boot).

> Or even better
> work together with Kris Moore so we don't have two solutions for the same task?

I'd like to open a discussion with Kris Moore on how we could go about detecting additional kernels.

Off the top of my head, here's a couple thoughts:

a. We could test a battery of different kernel names (kernel, kernel.bak, kernel.orig, etc.)
b. We could allow the user to set kernel1, kernel2, kernel3, etc. in loader.conf(5)
c. We could allow the user to set kernel="kernel1;kernel2;kernel3;..." in loader.conf(5)
d. Some combination of the above.
-- 
Devin

P.S. I think it'd also be nice to someday offer the user a choice of booting into a memory filesystem for rescue purposes. We've offered this to our users for years with the following configuration:

set root[0]=""
set root[1]="rescue_mfsroot"
set menu_caption[7][0]="Root Image: Default (1of2)"
set menu_caption[7][1]="Root Image: Rescue (2of2)"
set menu_caption[7]="${menu_caption[7][0]}"
set menu_command[7]="cycle_root"



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