File as generic block-device? - Kernel

This is a discussion on File as generic block-device? - Kernel ; Hi all, I have a project where I require to treat a file as a block-device (specifically, I want a file on an ext3 fs to act as one of the raid-members in a md-based stripe-set. I know that I ...

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Thread: File as generic block-device?

  1. File as generic block-device?

    Hi all,

    I have a project where I require to treat a file as a block-device
    (specifically, I want a file on an ext3 fs to act as one of the
    raid-members in a md-based stripe-set. I know that I can make a
    /filesystem/ on a file because both mkfs and mount (with -o loop) will
    accept a file as a block-device, but I have found no such function for
    mdadm, and am thus asking for a kernel-internal way to re-plug a file
    into the block-device layer.

    Is this possible?

    My current platform i CentOS5, a RHEL5 rebuild (modified 2.6.18-kernel).

    -S
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    Simen Thoresen - Dolphin ICS Systems Administrator
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  2. Re: File as generic block-device?

    Geert Uytterhoeven wrote:
    > On Wed, 22 Oct 2008, Simen Thoresen wrote:
    >> I have a project where I require to treat a file as a block-device
    >> (specifically, I want a file on an ext3 fs to act as one of the raid-members
    >> in a md-based stripe-set. I know that I can make a /filesystem/ on a file
    >> because both mkfs and mount (with -o loop) will accept a file as a
    >> block-device, but I have found no such function for mdadm, and am thus asking
    >> for a kernel-internal way to re-plug a file into the block-device layer.
    >>
    >> Is this possible?

    >
    > Sure! You just have to create the loop device (/dev/loop*) yourself using
    > losetup(8). `mount -o loop' does it itself behind your back.


    Ah! Perfect, thank you.

    -S

    > With kind regards,
    >
    > Geert Uytterhoeven
    > Software Architect
    >
    > Sony Techsoft Centre Europe
    > The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium
    >
    > Phone: +32 (0)2 700 8453
    > Fax: +32 (0)2 700 8622
    > E-mail: Geert.Uytterhoeven@sonycom.com
    > Internet: http://www.sony-europe.com/
    >
    > A division of Sony Europe (Belgium) N.V.
    > VAT BE 0413.825.160 · RPR Brussels
    > Fortis · BIC GEBABEBB · IBAN BE41293037680010



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    Simen Thoresen - Dolphin ICS Systems Administrator
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  3. Re: File as generic block-device?

    On Wed, 22 Oct 2008, Simen Thoresen wrote:
    > I have a project where I require to treat a file as a block-device
    > (specifically, I want a file on an ext3 fs to act as one of the raid-members
    > in a md-based stripe-set. I know that I can make a /filesystem/ on a file
    > because both mkfs and mount (with -o loop) will accept a file as a
    > block-device, but I have found no such function for mdadm, and am thus asking
    > for a kernel-internal way to re-plug a file into the block-device layer.
    >
    > Is this possible?


    Sure! You just have to create the loop device (/dev/loop*) yourself using
    losetup(8). `mount -o loop' does it itself behind your back.

    With kind regards,

    Geert Uytterhoeven
    Software Architect

    Sony Techsoft Centre Europe
    The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

    Phone: +32 (0)2 700 8453
    Fax: +32 (0)2 700 8622
    E-mail: Geert.Uytterhoeven@sonycom.com
    Internet: http://www.sony-europe.com/

    A division of Sony Europe (Belgium) N.V.
    VAT BE 0413.825.160 · RPR Brussels
    Fortis · BIC GEBABEBB · IBAN BE41293037680010

  4. Re: File as generic block-device?

    also sprach Simen Thoresen [2008.10.22.1456 +0200]:
    > accept a file as a block-device, but I have found no such function
    > for mdadm, and am thus asking for a kernel-internal way to
    > re-plug a file into the block-device layer.


    I suggest you search the web first.
    http://en.wikipedia.org/wiki/Loopback_disk_device

    --
    martin | http://madduck.net/ | http://two.sentenc.es/

    "you don't sew with a fork, so i see no reason
    to eat with knitting needles."
    -- miss piggy, on eating chinese food

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  5. Re: File as generic block-device?

    martin f krafft wrote:
    > also sprach Simen Thoresen [2008.10.22.1456 +0200]:
    >> accept a file as a block-device, but I have found no such function
    >> for mdadm, and am thus asking for a kernel-internal way to
    >> re-plug a file into the block-device layer.

    >
    > I suggest you search the web first.
    > http://en.wikipedia.org/wiki/Loopback_disk_device


    Thank you - I missed googling for the absolutely obvious.

    Sigh.

    -S



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