Transferring the root filesystem to a ramdisk?

From: Cordula's Web (cpghost_at_cordula.ws)
Date: 01/31/04

  • Next message: Bjorn Eikeland: "Re: Transferring the root filesystem to a ramdisk?" 
    To: freebsd-questions@freebsd.org
Date: Sat, 31 Jan 2004 15:08:33 +0100 (CET)

    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. 

    -- 
Cordula's Web. http://www.cordula.ws/
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  • Next message: Bjorn Eikeland: "Re: Transferring the root filesystem to a ramdisk?"

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