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Creating Filesystem using DD for LVM

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Operating Systems Linux Creating Filesystem using DD for LVM
# 1  
Old 01-25-2011
Creating Filesystem using DD for LVM
I created a new filesystem using dd and mounted:

I have a filesystem /FAW with 1Terra space
Code:
/dev/sdb1            1151331444  24742604 1068104612   3% /FAW



Steps I followed to create a new filesystem
Code:
# dd if=/dev/zero of=/FAW/vms/linux_vm/disk2.img bs=1 count=1024 seek=500G
# mke2fs disk2.img 

# mount -o loop disk2.img /FAW/xen_vm/

Now df -k output is :
==============

Code:
/FAW/vms/linux_vm/disk2.img
                     516061624     71448 489775776   1% /FAW/xen_vm


I want to be able to add the above disk2.img partition to pvcreate lvm which does not recognize.

Can someone tell me how i should convert it to filetype recognised by LVM.
# 2  
Old 01-25-2011
LVM, by default, ignores any "devices" outside of /dev, or anything with a filesystem on it. So the recommended (by me) way would be to run
Code:
# dd if=/dev/zero of=/FAW/vms/linux_vm/disk2.img bs=1 count=0 seek=500G
# losetup -sf /FAW/vms/linux_vm/disk2.img
# pvcreate /dev/loop<x>

where x is the number reported by losetup. Or, if there's no other data on it, use the whole of /dev/sdb1 for LVM.
# 3  
Old 01-25-2011
Hi Pludi,

Code:
# losetup -sf /FAW/vms/linux_vm/disk2.img
losetup: invalid option -- s

So i did:
Code:
losetup -f                                                # find unused
# losetup -f /FAW/vms/linux_vm/disk2.img

Still does not show up
Code:
# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2             9.7G  5.7G  3.5G  63% /
/dev/sda1             190M   45M  136M  25% /boot
/dev/sdb1             1.1T   24G 1019G   3% /FAW

/FAW/vms/linux_vm/disk2.img
                      493G   70M  468G   1% /FAW/xen_vm
# losetup -a
/dev/loop0: [fd01]:49160 (/FAW/vms/linux_vm/disk2.img)
/dev/loop2: [fd01]:49160 (disk2.img)


is there a way to make is use /dev/sdc1 ?
Last edited by pludi; 01-25-2011 at 09:04 AM..
# 4  
Old 01-25-2011
Of course it won't show up in df after losetup, since df shows only mounted filesystems. Remove the loopback you've just created, unmount /FAW/xen_vm, then set up the loopback device again and run pvcreate on it. After this it will still not show up in df, but you can create a volume group and logical volumes on it, which you can then put a filesystem on.
# 5  
Old 01-25-2011
Thanks a lot,

I think i made a mistake here.

After creating the disk
dd if=/dev/zero of=/FAW/vms/linux_vm/disk2.img bs=1 count=1024 seek=500G

I created a file system:

mke2fs disk2.img

After creating physical,logical volumes i again tried to create filesystem and it hanged.

mkfs.ext3 /dev/xen-vm/xen_prov
# 6  
Old 01-25-2011
Wait wait wait. The correct order is
  1. Create an image file
  2. Create a loopback device for the file
  3. Run pvcreate on the loopback device
  4. Run vgcreate on the "physical" volume
  5. Run lvcreate on the volume group
  6. Create a filesystem on the logical volume
  7. Mount the logical volume
Why did you create a filesystem on the image file? What were your exact steps and what does your system look like now?
# 7  
Old 01-27-2011
Sorry I am back to work just now, yesterday was a holiday for us.

I have not yet got the machine back to test it.

Ok here I am listing down what you said,

Code:
1) Create an image file
===============
#dd if=/dev/zero of=/FAW/vms/linux_vm/disk2.img bs=1 count=1024 seek=500G

Code:
2)Create a loopback device for the file
===========================
#losetup -f /FAW/vms/linux_vm/disk2.img


# losetup -a
/dev/loop0: [fd01]:49160 (/FAW/vms/linux_vm/disk2.img)

Code:
3) Run pvcreate on the loopback device
===============================
# pvcreate /dev/loop0  (initialise disk created)
  Physical volume "/dev/loop0" successfully created

Code:
4)Run vgcreate on the "physical" volume
===============================
#vgcreate xen-vm /dev/loop0
Volume group "xen-vm" successfully created

Code:
5) Run lvcreate on the volume group
============================
#lvcreate -L450G -nxen_prov xen-vm

Logical volume "xen_prov" created

Code:
6)Create a filesystem on the logical volume
===================================
#mkfs.ext3 /dev/xen-vm/xen_prov
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
58982400 inodes, 117964800 blocks
5898240 blocks (5.00%) reserved for the super user
First data block=0
......................
.........................................

Code:
7) Mount the logical volume
========================
mount /dev/xen-vm/xen_prov /FAW/xen_vm

Let us know if this is rite, I have not yet executed the 7th point since I have not go the system back yet.
Last edited by sriram003; 01-27-2011 at 06:25 AM.. Reason: correction point 7
This User Gave Thanks to sriram003 For This Post:
suryanarayan
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