[linux-lvm] lvremove is not deleting the file system

[linux-lvm] lvremove is not deleting the file system

[Guy Rouillier]

I'm using xen-create-image in an attempt to set up a new VM; host OS is 
Ubuntu Server 13.10, and I'm using LVM.  I failed in my first attempt 
due to my inexperience, so I changed some input parameters and I'm 
trying again.  The first attempt had successfully created the target LVM 
volumes for boot, root and swap, so I used lvremove to delete them.  All 
that went without error.

However, now when I try to run xen-create-image, I get the following 
error at the beginning when xen-create-image tries to create the target 
volumes:

Creating btrfs filesystem on /dev/dell-vg/oraclelinux-root
/dev/dell-vg/oraclelinux-root appears to contain an existing filesystem 
(btrfs).
Error: Use the -f option to force overwrite.
Running command 'mkfs.btrfs /dev/dell-vg/oraclelinux-root 2>&1' failed 
with exit code 256.
Aborting

I've tried searching for this error but can't find anything helpful. 
I've rerun this a dozen times and get the same result each time 
(deleting the created volumes and rebooting between each attempt.)  I 
looked in the /dev tree, and I see the dm node (dm-4) disappears after I 
run lvremove.  But apparently, lvremove doesn't delete the filesystem. 
So when I recreate the same volume in the same order, the filesystem is 
still there from the previous attempt.

How do I fix this?  Thanks.

-- 
Guy Rouillier

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Re: [linux-lvm] lvremove is not deleting the file system

[Sven Eschenberg]

Hi Guy,

This is not really a LVM problem I think. Basically lvremove only removes
a logical volume, which means, the metadata is discarded and the PEs are
released back into the allocation pool. It does not wipe the area (which
you somehow assumed as far as I understand your post).

Think of this, once you delete a partition table and recreate it with the
same layout, all filesystems will be available, if the drive was not
touched in any way.

The question seems to be: What is your actual intention?

Regards

-Sven

On Mon, December 30, 2013 01:58, Guy Rouillier wrote:
> I'm using xen-create-image in an attempt to set up a new VM; host OS is
> Ubuntu Server 13.10, and I'm using LVM.  I failed in my first attempt
> due to my inexperience, so I changed some input parameters and I'm
> trying again.  The first attempt had successfully created the target LVM
> volumes for boot, root and swap, so I used lvremove to delete them.  All
> that went without error.
>
> However, now when I try to run xen-create-image, I get the following
> error at the beginning when xen-create-image tries to create the target
> volumes:
>
> Creating btrfs filesystem on /dev/dell-vg/oraclelinux-root
> /dev/dell-vg/oraclelinux-root appears to contain an existing filesystem
> (btrfs).
> Error: Use the -f option to force overwrite.
> Running command 'mkfs.btrfs /dev/dell-vg/oraclelinux-root 2>&1' failed
> with exit code 256.
> Aborting
>
> I've tried searching for this error but can't find anything helpful.
> I've rerun this a dozen times and get the same result each time
> (deleting the created volumes and rebooting between each attempt.)  I
> looked in the /dev tree, and I see the dm node (dm-4) disappears after I
> run lvremove.  But apparently, lvremove doesn't delete the filesystem.
> So when I recreate the same volume in the same order, the filesystem is
> still there from the previous attempt.
>
> How do I fix this?  Thanks.
>
> --
> Guy Rouillier
>
> ---
> This email is free from viruses and malware because avast! Antivirus
> protection is active.
> http://www.avast.com
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] lvremove is not deleting the file system

[Alasdair G Kergon]

On Mon, Dec 30, 2013 at 02:46:45AM +0100, Sven Eschenberg wrote:
> Think of this, once you delete a partition table and recreate it with the
> same layout, all filesystems will be available, if the drive was not
> touched in any way.
 
Although lvcreate has a --zero option enabled by default that wipes
the beginning of the new device (and the next upstream release extends
this to wipe more signatures using libblkid).

You need to investigate precisely how your version of 'xen-create-image' is
using LVM and with which options.

Alasdair

Re: [linux-lvm] lvremove is not deleting the file system

[Alasdair G Kergon]

On Sun, Dec 29, 2013 at 07:58:04PM -0500, Guy Rouillier wrote:
> /dev/dell-vg/oraclelinux-root appears to contain an existing filesystem  
> (btrfs).
> Error: Use the -f option to force overwrite.

Does your version of xen-create-image offer a way to supply that -f?

If you're running lvremove yourself before retrying, look into running
wipefs manually on the device first.

Alasdair

Re: [linux-lvm] lvremove is not deleting the file system

[Sven Eschenberg]

On Mon, December 30, 2013 02:55, Alasdair G Kergon wrote:
> On Mon, Dec 30, 2013 at 02:46:45AM +0100, Sven Eschenberg wrote:
>> Think of this, once you delete a partition table and recreate it with
>> the
>> same layout, all filesystems will be available, if the drive was not
>> touched in any way.
>
> Although lvcreate has a --zero option enabled by default that wipes
> the beginning of the new device (and the next upstream release extends
> this to wipe more signatures using libblkid).

Forgot about that. Then again my documentation says zero wipes the first
KB, which does not really catch BTRFS sigs (which the OP uses) nor various
mdraid signatures.

I honestly hope the libblkid dependency will be optional ;-).

>
> You need to investigate precisely how your version of 'xen-create-image'
> is
> using LVM and with which options.

The actual OP, you meant. As you noted in your other post wipefs can come
in handy. Additionally blkid and lsblk are two things that come in handy,
to see what is going on.
>
> Alasdair
>

-Sven

Re: [linux-lvm] lvremove is not deleting the file system

[Guy Rouillier]

On 12/29/2013 9:00 PM, Alasdair G Kergon wrote:
> On Sun, Dec 29, 2013 at 07:58:04PM -0500, Guy Rouillier wrote:
>> /dev/dell-vg/oraclelinux-root appears to contain an existing filesystem
>> (btrfs).
>> Error: Use the -f option to force overwrite.
>
> Does your version of xen-create-image offer a way to supply that -f?

I tried supplying the -f option to xen-create-image.  Unfortunately, it 
did not alter the outcome.

>
> If you're running lvremove yourself before retrying, look into running
> wipefs manually on the device first.

Thank you, that solved the problem.  I was then able to run 
xen-create-image again and it recreated the LVs.  To answer Sven's 
question: "What is your actual intention?", I'm trying to rerun 
xen-create-image so that I can create this xen virtual machine. I could 
not do that because it failed trying to recreate the root LV.

-- 
Guy Rouillier

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Re: [linux-lvm] lvremove is not deleting the file system

[Sven Eschenberg]

I guess my question was somewhat misleading:

I was not sure, if you had some data to keep, or if you'd planned to trash
everything. Usually the warning about an existing FS is not a coincidence,
so better make sure, people really intend to wipe it ;-).

-Sven


On Mon, December 30, 2013 04:28, Guy Rouillier wrote:
> On 12/29/2013 9:00 PM, Alasdair G Kergon wrote:
>>
>> If you're running lvremove yourself before retrying, look into running
>> wipefs manually on the device first.
>
> Thank you, that solved the problem.  I was then able to run
> xen-create-image again and it recreated the LVs.  To answer Sven's
> question: "What is your actual intention?", I'm trying to rerun
> xen-create-image so that I can create this xen virtual machine. I could
> not do that because it failed trying to recreate the root LV.
>
> --
> Guy Rouillier
>
> ---
> This email is free from viruses and malware because avast! Antivirus
> protection is active.
> http://www.avast.com
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>