RFC: support for re-sourcing /etc/rc.conf

[Teske, Devin]

On Dec 2, 2013, at 10:45 AM, Colin Percival wrote:

> On 12/02/13 04:48, Hiroki Sato wrote:
>> Colin Percival <cperciva at freebsd.org> wrote:
>> cp> I'd like to commit the attached patch to /etc/rc.  When SIGALRM is received,
>> cp> it reloads /etc/rc.conf; this makes it possible for an rc.d script to perform
>> cp> first-boot system configuration and have it reflected by other rc.d scripts.
>> cp>
>> cp> In particular, this will allow me to provide EC2 user-data of
>> cp> 	>>/etc/rc.conf
>> cp> 	firstboot_pkgs_enable="YES"
>> cp> 	firstboot_pkgs_list="apache22"
>> cp> to an image with the sysutils/ec2-scripts and sysutils/firstboot-pkgs ports
>> cp> installed, and have a system running with apache22 installed moments later.
>> 
>> I am not familiar with sysutils/firstboot-pkgs and its use case, but
>> is it correct that packages are installed during /etc/rc and then
>> rc.conf will be updated before rc.d scripts for the installed
>> packages run from /etc/rc?  Where and when SIGALRM is sent from?
> 
> No, the other way around -- a different script (part of ec2-scripts) updates
> /etc/rc.conf based on metadata provided at VM launch time.  One use of this
> would be to set firstboot_pkgs_* variables to control the behaviour of the
> firstboot-pkgs port moments later in the boot process.
> 

sysrc(8) in 9.2+ base comes to mind.
NB: Available as a port for older releases 4.8+ (sysutils/sysrc)


> So:
> 1. VM image is created with ec2-scripts and firstboot-pkgs installed.
> 2. VM image is launched with user-data saying "I want apache22".

"bsdconfig startup_rcvar" in 9.2+ base comes to mind.
NB: Avaiable as a port for older releases 9.0+ (sysutils/bsdconfig)


> 3. Early in the boot process, ec2-scripts reads that user-data, updates
>   /etc/rc.conf, and signals /etc/rc.
> 4. /etc/rc re-sources /etc/rc.conf.

Cool. How's the signaling in #3 done to get #4?

Edit: Hiroki suggests using using /etc/rc.conf.d/{name}
Edit: "sysrc -f /etc/rc.conf.d/{name} firstboot_pkgs_{blah}=etc" comes to mind

> 5. Later in the boot process, firstboot-pkgs (having the new /etc/rc.conf
>   settings loaded) installs the apache22 package.
> 

/usr/share/bsdconfig/packages/packages.subr in 9.2+ base comes to mind.
Library for installing packages from a script (from any media device).

In 11.0-CURRENT, you have realtime API documentation:

	bsdconfig includes packages/packages

or more specifically...

	bsdconfig includes -dF package_add

Will display full description of the API function, f_package_add().

In 9.2-R or 9-STABLE (after SVN r252995), it uses pkg-tools.
In 10.0-BETA4 or 10-STABLE (after SVN r258420) or higher, it uses pkgng.

FYI:

I like the idea of firstboot_pkgs_*
I also like Hiroki's idea of stashing it all into rc.conf.d
-- 
Devin

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