Anatomy of the Linux Boot Process

Donna writes "This article discusses detailed similarities and differences involved in booting Linux on an x86-based platform (typically a PC-compatible SBC) and a custom embedded platform based around PowerPC, ARM, and others. It discusses suggested hardware and software designs and highlights the tradeoffs of each. It also describes important design pitfalls and best practices."

What a Debian system looks like when booting

[El Cubano]

http://seehuhn.de/comp/bootlog.html [seehuhn.de]

Originally posted on the debian-devel list: http://lists.debian.org/debian-devel/2004/11/msg00 547.html [debian.org]

Arrows

[Bios_Hakr]

I really hate to nit-pick, but any editor should have caught that the arrows in the flow chart point the wrong way.

Anyway, I've often wondered why the OS insists on redetecting hardware when BIOS does it for me already. I've heard that the LinuxBios actually does away with the hardware detect phase; leaving it solely to the kernel.

If the most popular OSes out there are taking care of HW at the high level, why haven't BIOS makers taken advantage of this to reduce their workload?

describes important design pitfalls

[Anonymous Coward]

Like, you know, a monolithic kernel?

Linux Boot

[jon855]

Now I understand the boot process much better, I always have started at the boot up process and wonder what the hell is Linux doing to my computer, eh, I guess I understand now better in how it boots, I want to see a comparsion between Linux and Windows... newb linux user here loves it but hates ATI support.

Re:The good thing about Linux

[Anonymous Coward]

Someone in my networking class in High School hotplugged a NIC once. Neither the nics, or the mainboard supported it. It also had windows 98.

It did't die. It actually detected it, installed the drivers, and the link went up. The old drivers simply threw up an "im not working" error in the device manager.

More discussion?

[mistersooreams]

The article makes an interesting read (although the server is getting slow already), but it seems a bit short on commentary. I'm no expert on the low-level systems of Linux, so the bare facts are quite interesting, but I would have been more interested to read a comparison of the merits of the different systems.

My impression, from the article, is that x86 versions of Linux are carrying quite a lot of legacy (from DOS et al). Does this mean that Linux on other architectures is "better" in any sense? I don't know, but I'd be interested if someone can inform.

don't like the splash screens

[LiquidMind]

i've noticed on SuSE that it now comes with a boot splash screen (a la Windows loading...). I know that's (somewhat) easily turned off, but really, I don't want my linux to be all fisher-price pretty. give me the rough and unadulterated command lines that are run when it boots up...make it look cool, make it intimidating, give it that matrix-esque feel...make it scare off all the n00bs that think they know everything.

Re:Speaking of linux booting...

[Claire-plus-plus]

Mandrake 10.1 doesn't have verbose as default. It has a boring little progress bar. However, I prefer verbose mode gives me something to read while my computer is booting.

Re:Arrows

[Anonymous Coward]

On a PCI system, the OS doesn't really "detect" hardware -- at least not in the old Win95 sense of poking registers to figure out what's there.

The OS just asks the BIOS for a list of PCI ID values, and loads the appropriate drivers for those IDs.

Re:What a Debian system looks like when booting

[El Cubano]

Or, you could post to the article that inspired yours(and was cited in it), regarding the Fedora boot process.

That was not my post. I just remember seeing it on debian-devel. Besides, the if you follow the links from the fedora-devel post you refer to, all you get is a couple of png images of the boot processes. The guy who did the Debian version explains how he did it and also provides links to the necessary tools.

Re:The good thing about Linux

[Anonymous Coward]

unsuccessfully tried hotswapping an AGP video card once... I spent the rest of the day looking up motherboard, ram, and video card prices online

Ah, it's not for softies, but hot-swapping a peripheral card has been done [folklore.org].

Re:Speaking of linux booting...

[SEE]

Bruce Tognazzini, founder the Apple Human Interface Group and fomer Apple Human Interface Evangelist, disagrees.

Some might be surprised to learn, however, that not only do I accept the idea of having flashing updates, such as "loading the kernel," I actually embrace it. First, it keeps the user engaged, and an engaged user is a happy user. Second, it informs. Yes, I'm aware that the only kernel most people are aware off is armed with eleven herbs and spices, but that's because no one has ever introduced them to the UNIX/LINUX kernel.

In ancient times, before there was disk, we all used tape cassettes to store our applications. We could literally hear them as they loaded into the computer over a period of one to three minutes. (Thank heavens today's hard disks are a million times faster so that, for example, Excel can load in only a few microseconds.) One might assume the sound of a loading program would be indistinguishable from random noise, but that proved not the case. Every application and every image had a unique signature. After a while, we could tell if we'd started the wrong program just by the sound of its code.

Today, few modem users understand handshaking protocols, but they do become used to a familiar pattern of clicks and screeches indicating normal vs. abnormal connections.

If regular folk can come to "understand" on some level the sound of high-speed binary code, do you think they cannot absorb some lessons from being subjected to new terminology like "kernel," etc.? Such terms so often come to be useful, as when some system software programmer spits out some horrifying message like, "fatal execution of kernel." At least they won't fear their supply of fried chicken is about to be cut off.

Entertain them. Teach them a little something, even if it seems "way over their heads." At the very least, it will keep them awake and alert.

bootchart site moved.

[Iamnoone]

A couple of other posts refer to this indirectly.
Bootchart is actually some of the coolest use of graphical display of data I have seen in a while:
bootchart [bootchart.org]
Some of the Solaris 10 guys even used it to improve the boot process on new releases of Solaris 10.
The latest updates (as of a few days ago) continued to streamline the system.

Re:Should be "BIOS" vs. "known hardware"

[renoX]

While you're right about the difference, the truth is: when you boot a PC, 99.99% of the time the hardware is identical to what it was the last time.

So it should be possible to store an HW description into a small flash and boot *fast*, without having to discover hardware, and if the user want to add new critical "cold-plug" hardware (such as boot disk), he would just have to hit Del at the boot, and then a HW discover would be made..