Configuring a new kernel is a dreaded task here. It seems I walk
through a bewildering array of stuff that when pressing F1 on them I
get more bewildering information I barely understand a word of.

For 8 or 9 yrs now I've mostly skirted the issue by using defaults.

I hnow the shortcoming is mine but still it is a massive amount of
knowledge needed to really know what most of those settings do.

Of course I know the easy ones but it appears thats never enough to
walk through and end up with a pared down but fully usable kernel.

In the end I usually just `genkernel all' and let ten thousand modules
be made and forget it.

I'd like to know more... enough so that when kernel config time rolls
around its not a frustrating and time consuming chore ... unless I go
the genkernel route.

I see plenty of howtos out there about kernel configuration but the
ones I've scanned or used take you through the steps but never really
teach you how to understand what all those setting do or entail.

I also realize that the kernel is a moving target and configurations
change literally with every kernel. But there must be a major base of
settings that change only slowly. Ones a user can learn enough about
that it isn't such a bewildering experience to try to get the settings
right in one or two goes.

And of course the kicker is that I'd like to learn this without weeks
and weeks of pounding away at it.

My current quest involved getting a kernel with full barrel iptables
and conn_track settings in place. The usual problem is that the howtos
are dealing with a much older (in kernel devel time) kernel that
actually has different or not all the setting currently available.

Can someone steer me to a more `in depth' tutorial? Or to something
they've found to really throw some light the chore? Not necessarily
about iptables but just the general chore of configuring a kernel
wisely.

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On Samstag, 5. Januar 2008, reader@newsguy.com wrote:

you want to read this:
http://www.kroah.com/lkn/

configuring a kernel is a matter of minutes. And seconds, if you just copy
over the old config and do 'make oldconfig'.

It is not hard - the first time read all the help texts and think about them.
That is the hardest part. Do you really need I2O? Almost nobody does. I2C?
Yes. ...

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On Saturday 05 January 2008, reader@newsguy.com wrote:
> Configuring a new kernel is a dreaded task here. It seems I walk
> through a bewildering array of stuff that when pressing F1 on them I
> get more bewildering information I barely understand a word of.

Ah yes. It's that way 'cause it was designed that way :-)

[snip]

> And of course the kicker is that I'd like to learn this without weeks
> and weeks of pounding away at it.

Unfortunately and in my experience, there's no easy shortcut to getting
a sane minimal kernel config. You really do need to have at least a
high-level understanding of what the various chunks of the kernel do so
that you can decide to enable them or not. You need to understand what
the various bits of hardware are - if you have never heard of iSCSI you
will have no idea if you need it or not. It's not enough to generally
just say "If you don't know what it is, you don't need it" as you might
run into SCSI, and know for a fact you do not have any SCSI hardware.
But, without it, all kinds of stuff break (like usb storage)

I know how I got my current level of knowledge - years and years of
pounding away at it, reading thousands of howtos and web pages, only to
have tons of it become redundant every six months. I strongly suspect
you may have to do something similar.

> My current quest involved getting a kernel with full barrel iptables
> and conn_track settings in place. The usual problem is that the
> howtos are dealing with a much older (in kernel devel time) kernel
> that actually has different or not all the setting currently
> available.

trial-and-error is probably your best bet. Get it working with a full
genkernel setup. Note which modules get used in real life, start
removing them in batches and make notes when stuff breaks

> Can someone steer me to a more `in depth' tutorial? Or to something
> they've found to really throw some light the chore? Not necessarily
> about iptables but just the general chore of configuring a kernel
> wisely.

I've yet to find a single resource for this. As I said above it does
seem to be a collection of knowledge gathered from many places over a
long period.

There's a reason for the existence of genkernel - it's so that you don't
have to go through all this pain and suffering, and can instead remove
stuff a bit at a time with reasonable confidence it won;t blow up in
your face :-)

alan

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alan dot mckinnon at gmail dot com
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"Hemmann, Volker Armin" <volker.armin.hemmann@tu-clausthal.de> writes:

> On Samstag, 5. Januar 2008, reader@newsguy.com wrote:
>
> you want to read this:
> http://www.kroah.com/lkn/

Thanks... I'm getting started now.

> configuring a kernel is a matter of minutes. And seconds, if you just copy
> over the old config and do 'make oldconfig'.

Yeah if you do that... but if you want to go through and look at all the
different stuff and try to understand.... the minutes, and seconds
theory is history.

> It is not hard - the first time read all the help texts and think about them.
> That is the hardest part. Do you really need I2O? Almost nobody does. I2C?
> Yes. ...

You are clearly on a much different plain than I.
`Read all the help texts and think about them.' If you can do that and
feel you've understood even a small portion of it, that puts you way
up the knowledge ladder compared to us lesser endowed.

Unless you mean all those places that say `if unsure just say yes'.
Or better yet those that say:
`There is no help available for this kernel option.'

Here is a good one.
CONFIG_PARAVIRT:
|
| Paravirtualization is a way of running multiple instances of
| Linux on the same machine, under a hypervisor. This option
| changes the kernel so it can modify itself when it is run
| under a hypervisor, improving performance significantly.
| However, when run without a hypervisor the kernel is
| theoretically slower. If in doubt, say N.

Unless you are talking about the last `If in doubt...'
Then you are stuck figuring out what on earth a hypervisor is.

Or here:

| CONFIG_HPET_TIMER:
|
| This enables the use of the HPET for the kernel's internal timer.
| HPET is the next generation timer replacing legacy 8254s.
| You can safely choose Y here. However, HPET will only be
| activated if the platform and the BIOS support this feature.
| Otherwise the 8254 will be used for timing services.

Unless you mean `You can safely choose Y here' then you have a few
days work figuring out what any of that means.

This goes on and on through the menus..
So no.. I don't think we are dealing with minutes here.

If you mean you can get it done if you just skip all of that.... then
yes it might be minutes.

If you wanted to pare down all the junk that is in a default
config... now you are taking days even weeks to get a handle on that.

At least it would be for the `intellectually challenged' like me..

Thanks again... that looks like a good start.

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On Samstag, 5. Januar 2008, reader@newsguy.com wrote:
> "Hemmann, Volker Armin" <volker.armin.hemmann@tu-clausthal.de> writes:
> > On Samstag, 5. Januar 2008, reader@newsguy.com wrote:
> >
> > you want to read this:
> > http://www.kroah.com/lkn/
>
> Thanks... I'm getting started now.
>
> > configuring a kernel is a matter of minutes. And seconds, if you just
> > copy over the old config and do 'make oldconfig'.
>
> Yeah if you do that... but if you want to go through and look at all the
> different stuff and try to understand.... the minutes, and seconds
> theory is history.

even than it does not take that ling.

>
> > It is not hard - the first time read all the help texts and think about
> > them. That is the hardest part. Do you really need I2O? Almost nobody
> > does. I2C? Yes. ...
>
> You are clearly on a much different plain than I.
> `Read all the help texts and think about them.' If you can do that and
> feel you've understood even a small portion of it, that puts you way
> up the knowledge ladder compared to us lesser endowed.

you have to start somewhere. When compiled my first kernel (2.2.14) nobody
hold my hand - and I needed several tries to get a booting one. But over the
years a lot of experience accumulates. Do I need fibrechannel? Certainly not.

>
> Unless you mean all those places that say `if unsure just say yes'.

is there better help? If you don't know what to do, say yes. Easy!

> Or better yet those that say:
> `There is no help available for this kernel option.'

there are only very few of those - and usually it is best to let them
unchanged.
>
> Here is a good one.
>
> CONFIG_PARAVIRT:
> | Paravirtualization is a way of running multiple instances of
> | Linux on the same machine, under a hypervisor. This option
> | changes the kernel so it can modify itself when it is run
> | under a hypervisor, improving performance significantly.
> | However, when run without a hypervisor the kernel is
> | theoretically slower. If in doubt, say N.
>
> Unless you are talking about the last `If in doubt...'
> Then you are stuck figuring out what on earth a hypervisor is.

Nope, the helptext tells you exactly what it does. And it tells you, that you
can say no, if you don't know what to do here.

>
> Or here:
> | CONFIG_HPET_TIMER:
> |
> | This enables the use of the HPET for the kernel's internal timer.
> | HPET is the next generation timer replacing legacy 8254s.
> | You can safely choose Y here. However, HPET will only be
> | activated if the platform and the BIOS support this feature.
> | Otherwise the 8254 will be used for timing services.
>
> Unless you mean `You can safely choose Y here' then you have a few
> days work figuring out what any of that means.

no, you have some SECONDS to figure it out:
gg:hpet
(with konqueror).
And what is wrong with 'you can safely choose Y here'? It tells you that it
does not harm to turn it on. So why turn it off? Why think about it, if you
don't know what a hpet is (btw, hpet is also explained in detail in the
Documentation directory. a single grep -R hpet /usr/src/linux/Documentation
would show you where).

>
> This goes on and on through the menus..
> So no.. I don't think we are dealing with minutes here.

you can, if you accept that you should use the recommended choice, expet when
ou knmow what you are doing.

>
> If you mean you can get it done if you just skip all of that.... then
> yes it might be minutes.
>
> If you wanted to pare down all the junk that is in a default
> config... now you are taking days even weeks to get a handle on that.

to de-junk a default config - even if you don't know what you do, is in realm
of half an hour to an hour. If you read everything.

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"Hemmann, Volker Armin" <volker.armin.hemmann@tu-clausthal.de> writes:

I think this is heading in direction different from what I intended.

You seem to be arguing that it can be done quickly... I don't disagree
with you. If like you say you mostly follow what ever is default
unless you know what you are doing. But if that is what you do then
genkernel is even quicker... Not in compile time but to decide is not
more than `genkernal all'.

So I haven't been saying it can't be done quickly. (If you depend
largely on defaults). The os designers have seen to it that the
defaults will produce a working kernel. And they are pretty good at
it.

I'm not complaining that the process provided is overly hard. (If you
mostly follow defaults)

In the very first post I said:

>> For 8 or 9 yrs now I've mostly skirted the issue by using defaults.

That is all you suggest too. Skirt the issue by using defaults.

>> If you wanted to pare down all the junk that is in a default
>> config... now you are taking days even weeks to get a handle on that.
>
> to de-junk a default config - even if you don't know what you do, is
> in realm of half an hour to an hour. If you read everything.

Do you have a de-junked .config that I can diff against the
default.. it would be a way to see what kinds of things get dropped.

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reader@newsguy.com wrote:
> Configuring a new kernel is a dreaded task here. It seems I walk
> through a bewildering array of stuff that when pressing F1 on them I
> get more bewildering information I barely understand a word of.
>
> < SNIP >
>
> Can someone steer me to a more `in depth' tutorial? Or to something
> they've found to really throw some light the chore? Not necessarily
> about iptables but just the general chore of configuring a kernel
> wisely.
>
>

The first time is the hardest one. I did a make mrproper then ran make
menuconfig and just got started. The third time the kernel booted up at
least. The biggest thing is getting the file systems, drivers for your
drive controller and other critical things that are needed to boot up.
After that, you can add them as needed.

If you get a kernel that boots up fine and allows you to do things, save
it. I almost always have a couple old kernels laying around /boot.
That way if the current one gets corrupt or something, you can at least
fall back on a old one. That may not help if /boot is corrupt but you
get the idea. Here is my saved one and how I name them:

root@smoker / # ls -al /boot/bzImage-2.6.*
-rw-r--r-- 1 root root 2189488 2007-01-04 18:01
/boot/bzImage-2.6.18.gentoo-r6-1
-rw-r--r-- 1 root root 2357808 2007-06-08 05:47 /boot/bzImage-2.6.20-r8-1
-rw-r--r-- 1 root root 2389616 2007-06-08 07:01 /boot/bzImage-2.6.20-r8-2
-rw-r--r-- 1 root root 2396880 2007-06-13 01:53 /boot/bzImage-2.6.20-r8-3
-rw-r--r-- 1 root root 2417840 2007-08-31 23:10 /boot/bzImage-2.6.22-r5
-rw-r--r-- 1 root root 2421840 2007-11-25 13:26 /boot/bzImage-2.6.22-r9-1
-rw-r--r-- 1 root root 2437912 2007-12-18 04:25 /boot/bzImage-2.6.23-r3-1
root@smoker / #

The last number is the revision of that specific version. You may
notice it takes even me a couple times to get it right.

You may find that just like with the tutorials you have read, you are
going to be told different ways to do about everything. Each of us have
our own ways of doing things based on past experiences. Apply what
needs to be applied to your situation and keep it sane.

Hope this little bit of info helps.

Dale

:-) :-) :-)
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Hemmann, Volker Armin wrote:
> On Samstag, 5. Januar 2008, reader@newsguy.com wrote:
>
> you want to read this:
> http://www.kroah.com/lkn/
>
> configuring a kernel is a matter of minutes. And seconds, if you just copy
> over the old config and do 'make oldconfig'.
>
> It is not hard - the first time read all the help texts and think about them.
> That is the hardest part. Do you really need I2O? Almost nobody does. I2C?
> Yes. ...
>
>

Yea, it usually only take me a few minutes to do one from scratch too.
It's not to bad. Some things have moved tho.

Dale

:-) :-)
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On Saturday 05 January 2008, reader@newsguy.com wrote:
> > to de-junk a default config - even if you don't know what you do,
> > is in realm of half an hour to an hour. If you read everything.
>
> Do you have a de-junked .config that I can diff against the
> default.. it would be a way to see what kinds of things get dropped.

Drivers for stuff you don't need and you will likely never use. Like ham
radio stuff, v4linux (first version), I20, on a notebook all the
enterprise-grade connect-a-machine-to-storage-stuff like iSCSI and
Infiniband, all of ISA and MCA and the pre-pci bus drivers, old disk
types like mfm and on modern boards usually even IDE as well.

Removing all these unused drivers is the single largest improvement in
reducing kernel size. The general rule with drivers is that if you are
familiar with YOUR hardware and you've never heard of something in the
config then you don't have it and don't need it :-)

Complete kernel sub-systems are a bit harder, although some are still
obvious. Like virtualisation. I assure you that if you have never heard
of kvm and paravirt, then you certainly don't need it.

With other stuff I usually end up leaving them in and removing things
gradually as I compile the next kernel and learn more about stuff out
there. If say HPET intrigues you and you want to know more, then Google
it. Tomorrow you can do another one.

Like I said in an earlier mail, it's not an easy process. It's only easy
if you know most of it already - like Volker. I'd guess he has long
since forgotten what it took to learn everything he knows, so of
course "It's obvious!"...

Comparing his and your configs is mostly pointless as your machines will
differ considerably. The config file is >70k and even on two recent
standard ubuntu configs the differences are over 1000 lines. Good luck
with comparing that lot and trying to figure out what's going on :-)

alan

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alan dot mckinnon at gmail dot com
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reader@newsguy.com skrev:
> Then you are stuck figuring out what on earth a hypervisor is.
>
Alt+F2
wp:hypervisor
ENTER

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