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Hardware found at install, mostly in initrd or where else?

 
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formatix



Joined: Sat Nov 03, 2007 11:39 am
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PostPosted: Tue Jul 20, 2010 12:55 am    Post subject: Hardware found at install, mostly in initrd or where else? Reply with quote

I'm wondering about the location of the localized hardware found at install time. You know, what's essentially seen in boot.log or dmesg and then where that "knowledge" is kept by the installation.

I've read - and done it- that a Linux hdd can be removed and put in a different pc and it will boot up with -usually- all the correct driver/modules loaded. And of course that's all seen under /proc and /sys but these are dynamic and so will change anyway.

I know that some distros will use the /var/lib/hardware... which shows up all the system bus and drives info. And /etc will have appropriate directories used for the graphics/xorg and sound card. Plus, sometimes script files are used in /init or /rcd to load specific modules for the hardware.

Aside from these, is the initrd file the keeper of this info?

The /var/lib/hardware... entries, would they be referred to by the system at any time when doing any major updating/upgrading?

And a question which all this is leading up to: should editing of some of the parameters in certain /var/lib/hardware... files allow influence on how that hardware is used, maybe in conjunction with udev rules?
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nelz
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Joined: Mon Apr 04, 2005 12:52 pm
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Location: Warrington, UK

PostPosted: Wed Jul 21, 2010 9:12 pm    Post subject: Reply with quote

The initrd only takes care of initialising the basic hardware needed for the kernel to proceed. this is things like disk controller drivers and filesystems, so that the boot can proceed from your hard disk. Hardware recognition is mainly looked after by hal and the kernel. I don't have a /var/lib/hardware on any of my computers, so that clearly isn't critical.
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roseway
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Joined: Thu Jan 18, 2007 2:27 pm
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PostPosted: Thu Jul 22, 2010 7:45 am    Post subject: Reply with quote

HAL is deprecated nowadays, and most systems are moving (or have moved) to udev. Apart from the essential start-up hardware, it's all autodetected during booting.
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nelz
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PostPosted: Thu Jul 22, 2010 9:37 am    Post subject: Reply with quote

HAL is deprecated, but is still in use by most systems. Udev has taken some of the job over, and there will be a HAL replacement in due course, but HAL is still in use quite a lot.

The main part of the hardware detection is handled by the kernel though, whether this information is then used by HAL, Udev or TNBT is less relevant.
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formatix



Joined: Sat Nov 03, 2007 11:39 am
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PostPosted: Sat Jul 24, 2010 9:36 am    Post subject: Reply with quote

So,my questions were redundant, there being no user influence over any hardware detected?

I don't count maybe a "mod alias xxxx" for a soundcard or assigning static ip to nics or small tweaks to xorg.conf as much influence.
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nelz
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PostPosted: Sun Jul 25, 2010 9:20 pm    Post subject: Reply with quote

No real influence of what is detected, only over how it is handled once it is detected. You've already mentioned xorg.conf (or xorg.conf.d files for later XOrg releases) but udev rules can also be used to alter the behaviour of the system when something is detected.

As can HAL's fdi files, but those are godawful abominations that are dying none too soon.
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