I'm trying to follow the stemcell instructions for brtfs [1] which involves
creating a large btrfs.img file using dd command.

I am trying to create it on a large volume, rather than the small root
mount that I have on my AWS VM; but the following command is unmounting the
mounted volume:

I have a 32G volume at /var/vcap/store, and /var/vcap/store/tmp already
exists, and I am running

dd if=/dev/zero of=/var/vcap/store/tmp/btrfs.img bs=1M count=10k

If I check df shortly after starting this command, the /var/vcap/store
mount has disappeared.

Is this a feature/bug of dd? How can I stop it doing this?

[1]
https://github.com/cloudfoundry/bosh/blob/master/bosh_agent/misc/stemcell/build2/README.md#creating-a-btrfs-filesystem

--
Dr Nic Williams
Stark & Wayne LLC - consultancy for Cloud Foundry users
http://drnicwilliams.com
http://starkandwayne.com
cell +1 (415) 860-2185
twitter @drnic

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  • Martin Englund at Feb 18, 2013 at 4:52 pm
    Just add another volume, attach it and use that instead - that's what I've done

    /M

    On Mon, Feb 18, 2013 at 8:41 AM, Dr Nic Williams
    wrote:
    I'm trying to follow the stemcell instructions for brtfs [1] which involves
    creating a large btrfs.img file using dd command.

    I am trying to create it on a large volume, rather than the small root mount
    that I have on my AWS VM; but the following command is unmounting the
    mounted volume:

    I have a 32G volume at /var/vcap/store, and /var/vcap/store/tmp already
    exists, and I am running

    dd if=/dev/zero of=/var/vcap/store/tmp/btrfs.img bs=1M count=10k

    If I check df shortly after starting this command, the /var/vcap/store mount
    has disappeared.

    Is this a feature/bug of dd? How can I stop it doing this?

    [1]
    https://github.com/cloudfoundry/bosh/blob/master/bosh_agent/misc/stemcell/build2/README.md#creating-a-btrfs-filesystem

    --
    Dr Nic Williams
    Stark & Wayne LLC - consultancy for Cloud Foundry users
    http://drnicwilliams.com
    http://starkandwayne.com
    cell +1 (415) 860-2185
    twitter @drnic


    --
    cheers,
    /Martin
    --
    Martin Englund, Staff Engineer, Cloud Foundry, VMware Inc.
    "The question is not if you are paranoid, it is if you are paranoid enough."
  • Dr Nic Williams at Feb 18, 2013 at 8:00 pm
    Doh! That'll teach me for cargo culting some instructions from a README :)
    On Monday, February 18, 2013, Martin Englund wrote:

    Just add another volume, attach it and use that instead - that's what I've
    done

    /M

    On Mon, Feb 18, 2013 at 8:41 AM, Dr Nic Williams
    <drnicwilliams@gmail.com <javascript:;>> wrote:
    I'm trying to follow the stemcell instructions for brtfs [1] which involves
    creating a large btrfs.img file using dd command.

    I am trying to create it on a large volume, rather than the small root mount
    that I have on my AWS VM; but the following command is unmounting the
    mounted volume:

    I have a 32G volume at /var/vcap/store, and /var/vcap/store/tmp already
    exists, and I am running

    dd if=/dev/zero of=/var/vcap/store/tmp/btrfs.img bs=1M count=10k

    If I check df shortly after starting this command, the /var/vcap/store mount
    has disappeared.

    Is this a feature/bug of dd? How can I stop it doing this?

    [1]
    https://github.com/cloudfoundry/bosh/blob/master/bosh_agent/misc/stemcell/build2/README.md#creating-a-btrfs-filesystem
    --
    Dr Nic Williams
    Stark & Wayne LLC - consultancy for Cloud Foundry users
    http://drnicwilliams.com
    http://starkandwayne.com
    cell +1 (415) 860-2185
    twitter @drnic


    --
    cheers,
    /Martin
    --
    Martin Englund, Staff Engineer, Cloud Foundry, VMware Inc.
    "The question is not if you are paranoid, it is if you are paranoid
    enough."

    --
    Dr Nic Williams
    Stark & Wayne LLC - consultancy for Cloud Foundry users
    http://drnicwilliams.com
    http://starkandwayne.com
    cell +1 (415) 860-2185
    twitter @drnic

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postedFeb 18, '13 at 4:41p
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