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Date:      Sat, 31 Jan 2004 15:29:22 +0100
From:      Bjorn Eikeland <bjorn@eikeland.info>
To:        cpghost@cordula.ws, "freebsd-multimedia@freebsd.org" <freebsd-multimedia@freebsd.org>
Subject:   Re: Transferring the root filesystem to a ramdisk?
Message-ID:  <opr2m868m9omdbx5@localhost>
In-Reply-To: <20040131140833.69B9540823@fw.farid-hajji.net>
References:  <20040131140833.69B9540823@fw.farid-hajji.net>

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I'm probably in over my head here, but;
chroot should change the root filesystem for you.
(look in the manpages for more details)

As for powering down the hdd I did find a page for this,
but havent had time to play with it yet:
http://www.cran.org.uk/bruce/software.php

best of luck!

> Hello,
>
> in an attempt to save power on FreeBSD servers, I'm
> trying to replace the hdd with a ramdisk. The idea is to:
>
>   1. boot from the hdd (or netboot from an NFS server)
>   2. configure a ram disk (md(4))
>   3. copy everything that's needed to ram disk
>   4. transfer kernel root to ramdisk (*)
>   5. turn off the hdd (**)
>
> (*) is the hairy question.
> (**) How can that be done?
>
> I won't need paging, because there'll be enough ram for
> everything (ramdisk, kernel and userland).
>
> Now the questions are:
>
>   * How to "attach" the root filesystem to the ram disk?
>
>     Can this be done only through pxe/netboot before the
>     kernel starts, or is there some kind of system call
>     that can transfer root on a running system?
>
>   * How to power off (and on) the hdd (both for ATA and SCSI)?
>
>   * Will the power consumption decrease (no hdd) or will
>     it increase (more ram)? Anybody measured this before
>     with regular diskless machines?
>
> Thanks,
> -cpghost.
>




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