4:03 p.m.
Hello
I use XEN on Fedora 8 with Domu on a LVM partition.
Before, on Fedora Core 6, I could backup each Domu by directly mounting
the filesystem of the Domu (mount /dev/vg00/lvfoo /mnt) and then running
dump on it.
On Fedora 8, I can't mount directly the filesystem of the Domu, so I
backup the filesystem of the Domu using the dd command (dd
if=/dev/vg00/lvfoo of=/var/xen/lvfoo.img)
But the backup with dd is longer and takes more disk space than the
backup with dump, as dd copies unused blocks.
Is there a better method to backup a Domu filesystem from Dom0 on Fedora 8 ?
Thanks in advance
Anne Facq
4:19 p.m.
New subject: How to backup a Domu filesystem (on LVM) from Dom0 on Fedora 8 ?
Anne Facq wrote:
Hello
I use XEN on Fedora 8 with Domu on a LVM partition.
Before, on Fedora Core 6, I could backup each Domu by directly mounting
the filesystem of the Domu (mount /dev/vg00/lvfoo /mnt) and then running
dump on it.
On Fedora 8, I can't mount directly the filesystem of the Domu, so I
Pardon if this is a dumb question, but why not?
backup the filesystem of the Domu using the dd command (dd
if=/dev/vg00/lvfoo of=/var/xen/lvfoo.img)
But the backup with dd is longer and takes more disk space than the
backup with dump, as dd copies unused blocks.
Is there a better method to backup a Domu filesystem from Dom0 on Fedora
8 ?
I suppose you could use the img2qcow tool (possibly directly on
/dev/vg00/lvfoo) to get a qcow file instead of a raw image. However, I
vaguely remember seeing somewhere that the qcow created by the xen tools
is not necessarily 100% compatible with other qcow tools.
HTH,
Aaron
5:35 p.m.
New subject: How to backup a Domu filesystem (on LVM) from Dom0 on Fedora 8 ?
Aaron Clark wrote:
Anne Facq wrote:
> Hello
>
> I use XEN on Fedora 8 with Domu on a LVM partition.
>
> Before, on Fedora Core 6, I could backup each Domu by directly
> mounting the filesystem of the Domu (mount /dev/vg00/lvfoo /mnt) and
> then running dump on it.
>
> On Fedora 8, I can't mount directly the filesystem of the Domu, so I
Pardon if this is a dumb question, but why not?
Because in Dom0 the device for a paravirt Domu (/dev/vg00/lvfoo in my
case) is mapped to a virtual disk /dev/xvda (I created the Domu with
virt-install), and the only way I found to mount this Domu filesystem,
is to :
- get the size of the boot sector of /dev/vg00/lvfoo
(with fdisk -ul /dev/vg00/lvfoo)
= 63
- compute the offset (multiply by block size)
- specify this offset to the mount command :
mount -o offset=32256 /dev/vg00/lvfoo /mnt/
As I can't specify an offset to dump, the command "dump 0 -f lvfoo.dump
/mnt" doesn't work.
> backup the filesystem of the Domu using the dd command (dd
> if=/dev/vg00/lvfoo of=/var/xen/lvfoo.img)
> But the backup with dd is longer and takes more disk space than the
> backup with dump, as dd copies unused blocks.
>
> Is there a better method to backup a Domu filesystem from Dom0 on
> Fedora 8 ?
I suppose you could use the img2qcow tool (possibly directly on
/dev/vg00/lvfoo) to get a qcow file instead of a raw image. However, I
vaguely remember seeing somewhere that the qcow created by the xen tools
is not necessarily 100% compatible with other qcow tools.
Thanks for you help, I'm going to have a look at it.
Regards,
Anne Facq
2:58 a.m.
New subject: How to backup a Domu filesystem (on LVM) from Dom0 on Fedora 8 ?
Anne Facq wrote:
Because in Dom0 the device for a paravirt Domu (/dev/vg00/lvfoo in
my
case) is mapped to a virtual disk /dev/xvda (I created the Domu with
virt-install), and the only way I found to mount this Domu filesystem,
is to :
- get the size of the boot sector of /dev/vg00/lvfoo
(with fdisk -ul /dev/vg00/lvfoo)
= 63
- compute the offset (multiply by block size)
- specify this offset to the mount command :
mount -o offset=32256 /dev/vg00/lvfoo /mnt/
Uh, oh, quite complicated and error prone. Can be done much easier.
Option (1): Use kpartx, it will create device mapper mappings for your
partitions. Try "kpartx -v -a /dev/vg00/lvfoo", should give you
/dev/vg00/lvfoop[1234]. "kpartx -d ... " removes the mappings.
Option (2): (works only with xen kernel): Configure the device as
virtual disk *in Domain-0*: "xm block-attach 0 phy:/dev/vg00/lvfoo xvda
w". Gives you /dev/xvda[1234]. "xm block-detach ..." removes it.
HTH,
Gerd
2 a.m.
New subject: How to backup a Domu filesystem (on LVM) from Dom0 on Fedora 8 ?
Gerd Hoffmann wrote:
Anne Facq wrote:
> Because in Dom0 the device for a paravirt Domu (/dev/vg00/lvfoo in my
> case) is mapped to a virtual disk /dev/xvda (I created the Domu with
> virt-install), and the only way I found to mount this Domu filesystem,
> is to :
> - get the size of the boot sector of /dev/vg00/lvfoo
> (with fdisk -ul /dev/vg00/lvfoo)
> = 63
> - compute the offset (multiply by block size)
> - specify this offset to the mount command :
> mount -o offset=32256 /dev/vg00/lvfoo /mnt/
Uh, oh, quite complicated and error prone. Can be done much easier.
Option (1): Use kpartx, it will create device mapper mappings for your
partitions. Try "kpartx -v -a /dev/vg00/lvfoo", should give you
/dev/vg00/lvfoop[1234]. "kpartx -d ... " removes the mappings.
Option (2): (works only with xen kernel): Configure the device as
virtual disk *in Domain-0*: "xm block-attach 0 phy:/dev/vg00/lvfoo xvda
w". Gives you /dev/xvda[1234]. "xm block-detach ..." removes it.
Many thanks for this solution, it helps me a lot.
If this can help someone, here are the steps to backup a Domu
(filesystem on LVM in backend and on xvda in frontend) with the dump
command from Dom0 (Fedora 8), using one of the 2 solutions you advised,
kpartx :
----------------------------------------------------------------
# The DomU named "foo" must be stopped before dump
xm shutdown -w foo
# Creates device mapper mappings /dev/mapper/lvfoop[1234] for
/dev/vg00/lvfoo
kpartx -v -a /dev/vg00/lvfoo
# Mounts temporarly the filesystem to backup
mount /dev/mapper/lvfoop1 /mnt/lvfoo/
# Launches the dump
/sbin/dump 0 -L FULL_foo -f /BACKUP-XEN/foo.colddump /mnt/lvfoo/
# Umount the filesystem
umount /mnt/lvfoo/
# Removes the mappings
kpartx -d /dev/vg00/lvfoo
# Unmount the filesystem
umount /mnt/lvfoo
# The DomU can now be restarted
xm create --config /var/lib/xend/....
----------------------------------------------------------------
Regards,
Anne Facq
3:18 a.m.
New subject: How to backup a Domu filesystem (on LVM) from Dom0 on Fedora 8 ?
Anne Facq <annefacq(a)crpp-bordeaux.cnrs.fr> writes:
Aaron Clark wrote:
> Anne Facq wrote:
>> Hello
>>
>> I use XEN on Fedora 8 with Domu on a LVM partition.
>>
>> Before, on Fedora Core 6, I could backup each Domu by directly
>> mounting the filesystem of the Domu (mount /dev/vg00/lvfoo /mnt)
>> and then running dump on it.
>>
>> On Fedora 8, I can't mount directly the filesystem of the Domu, so
>> I
>
> Pardon if this is a dumb question, but why not?
Because in Dom0 the device for a paravirt Domu (/dev/vg00/lvfoo in my
case) is mapped to a virtual disk /dev/xvda (I created the Domu with
virt-install), and the only way I found to mount this Domu filesystem,
is to :
- get the size of the boot sector of /dev/vg00/lvfoo
(with fdisk -ul /dev/vg00/lvfoo)
= 63
- compute the offset (multiply by block size)
- specify this offset to the mount command :
mount -o offset=32256 /dev/vg00/lvfoo /mnt/
As I can't specify an offset to dump, the command "dump 0 -f lvfoo.dump
/mnt" doesn't work.
Shot from the hip: losetup with the offset?
[...]
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5 comments
4 participants
participants (4)
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Aaron Clark -
Anne Facq -
Gerd Hoffmann -
Markus Armbruster