Re: updating kernel to 2.6.13-rc1 from 2.6.12 + CONFIG_DEVFS_FS + empty /dev

From: Willy Tarreau (willy_at_w.ods.org)
Date: 07/02/05

  • Next message: Eric Valette: "Re: updating kernel to 2.6.13-rc1 from 2.6.12 + CONFIG_DEVFS_FS + empty /dev" 
    Date:	Sat, 2 Jul 2005 10:22:18 +0200
To: Eric Valette <eric.valette@free.fr>

    Hi Eric,

    On Sat, Jul 02, 2005 at 09:22:20AM +0200, Eric Valette wrote:
    > Greg KH wrote:
    >
    > > Why? Why not put it in ROM with your kernel image, look at how the
    > > kernel build process does it with the "built-in" initramfs.
    >
    > Well, nowadays, most system have only flash because ROM does not enable
    > to do firmware upgrade. Second, putting it in the kernel or as a
    > separate flash section or in an initrd does not change the problem :
    > something has to be stored on non volatile memory whereas you do not
    > need that for devfs (except devfs code itself of course) but then you
    > have udev instead of devfs...

    Well, although I've never used udev because I've been using sort of an
    equivalent called "preinit" for 4 years now, I don't totally agree with
    you about the firmware upgrade : when you package your systems to allow
    the customer to perform "firmware" upgrades, your image is already very
    specific to a hardware model, and I don't see why you would need to
    create /dev entries independantly from the kernel or rootfs. Speaking
    for myself, my .preinit script which describes how to fill /dev entries
    is on the rootfs and does not need to change once packaged.

    However, I agree that I encountered difficulties using this system on
    more generic hardware, because sometimes the raid devices did not exist,
    or things like this caused trouble.

    IMHO, a generic system should use a full /dev directory and an embedded
    system should use just the strict minimum necessary for the specific
    hardware to run.

    > > I boot my boxes with nothing in /dev and have been for almost a year
    > > now. udev works just fine for this, and so do some other programs that
    > > work like udev does.
    >
    > Nothing in /dev but with initramfs. Same cost...
    >
    > BTW : valette@tri-yann->df /dev
    > Filesystem 1K-blocks Used Available Use% Mounted on
    > tmpfs 10240 2876 7364 29% /dev
    >
    >
    > 2 MB RAM on my PC??? I must be missing something.

    I think something went wrong, perhaps something like

       # some_prog >/dev/null

    while null did not exist. My /dev is a tmpfs too, but mounted with size=0,
    so that I can only create inodes into it, but cannot write any data. One
    other advantage of using size=0 is that "df" does not show it by default.

    Cheers,
    Willy

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  • Next message: Eric Valette: "Re: updating kernel to 2.6.13-rc1 from 2.6.12 + CONFIG_DEVFS_FS + empty /dev"

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