KVM Snapshot/Backup Script

stacksofplates

So I posted a snapshot export script on here a long time ago, and it wasn't really correct. It created an overlay disk of a backing store and exported the backing store. Red Hat doesn't include the most up to date version of QEMU, so they can push RHEV. RHEL/CentOS 7 only comes with QEMU 1.5, and for live snapshots you need at least 2.0. So if you ad the oVirt repos you can get the newest version with the package qemu-kvm-rhev, or use Fedora server. Here's a script I wrote to take a live external snapshot and compress it to a location. I used my normal template with the interactive function. vmLocation is the location of your VMs. I usually keep mine in the same area. I should add full paths for everything, but I'm lazy this evening. I'll add them later. I also need to add some error handling but this is a rough start if anyone needs to use it.

#!/bin/bash


vmLocation="/data/VMs"

today=$(date +%m-%d-%Y)



#Script functions
function script_help () {
  echo "
      Usage: $(basename $0) [options] dom-name snap-name save-location disk-name

          -i   Ineractive mode

          -h   this help text

          dom-name        Name of domain to take snapshot of

          snap-name       Name of snapshot

          save-location   location to copy snapshot to

          disk-name       Name of disk in VM

      Example:
        $(basename $0) bind-server bind-snap01 /export/snaps/ vda"

  exit ${1:-0}
}

function interactive_snap () {

  echo "Domain name"
  read name

  echo "Snapshot name"
  read snap

  echo "Location to save snap"
  read location

  echo "Disk name"
  read disk

  virsh dumpxml $name > $location/$name.xml

  diskPath=$(virsh domblklist $name | grep -i $disk | awk '{ print $2 }')

  virsh snapshot-create-as --domain $name $snap --diskspec $disk,file=$vmLocation/$snap.qcow2 --disk-only --atomic

  tar -czvf $location/$snap-$today.tar.gz $diskPath

  virsh blockcommit $name $disk --active --verbose --pivot

  rm -f $vmLocation/$snap.qcow2

  virsh snapshot-delete --metadata $name $snap

  exit ${1:-0}

}

function argument_snap () {

  virsh dumpxml $name > $location/$name.xml

  diskPath=$(virsh domblklist $name | grep -i $disk | awk '{ print $2 }')

  virsh snapshot-create-as --domain $name $snap --diskspec $disk,file=$vmLocation/$snap.qcow2 --disk-only --atomic

  tar -czvf $location/$snap-$today.tar.gz $diskPath

  virsh blockcommit $name $disk --active --verbose --pivot

  rm -f $vmLocation/$snap.qcow2

  virsh snapshot-delete --metadata $name $snap

  exit ${1:-0}



}

#Show help if no arguments or options are passed
[[ ! "$*" ]] && script_help 1
OPTIND=1


#Read command line options
while getopts "ih" opt; do
    case "$opt" in
      i) interactive_snap ;;
      h) script_help ;;
      \?) script_help 1 ;;
    esac
done
shift $(($OPTIND-1));

#Run argument function
name=$1
snap=$2
location=$3
disk=$4
argument_snap

matteo nunziati

@stacksofplates maybe of interest: my libvirt backup wrapper

Romo

@stacksofplates this basically is a super fast clone of the original vm using snapshots?

Romo

I haven't used external snapshots for anything, but now that I am reading about them I should be using them more.

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates this basically is a super fast clone of the original vm using snapshots?

It takes a snapshot, which directs writes to the new file. Then tars and gzips the backing store (original disk image) to wherever you put in for the location, and then merges the snapshot back into the backing store.

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

I haven't used external snapshots for anything, but now that I am reading about them I should be using them more.

I still use internal for things like updates and large changes, but the external ones are nice.

Romo

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates this basically is a super fast clone of the original vm using snapshots?

It takes a snapshot, which directs writes to the new file. Then tars and gzips the backing store (original disk image) to wherever you put in for the location, and then merges the snapshot back into the backing store.

This is too keep the system live during the backup?

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates this basically is a super fast clone of the original vm using snapshots?

It takes a snapshot, which directs writes to the new file. Then tars and gzips the backing store (original disk image) to wherever you put in for the location, and then merges the snapshot back into the backing store.

This is too keep the system live during the backup?

Right. If you don't do it this way, you have to either shut the VM down or suspend it.

Romo

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that. However, it does make a nice VDI tool. If you have an image and do qemu-img create -b and use it as the backing file, the overlays spin up really quickly. Like less than a second. But you can't write to the backing file as long as there are overlay files reading from it.

stacksofplates

I create the template, and run virt-sysprep on it. Then I can update the disk with virt-sysprep --update. It automatically spins up a temp VM that updates all of the packages in the disk. But if you do this, you need to run virt-sysprep --selinux-relabel so it relabels the disk on the next clone. If not, labels can get screwed up;

Romo

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that.

My clones take 30-40 seconds, how do you thin provision? Using virt-sparsify on an image?

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that.

My clones take 30-40 seconds, how do you thin provision? Using virt-sparsify on an image?

No, qcow2 is thin by default. But all of my templates are RHEL systems. So the OS doesn't use hardly any space. Are you cloning Windows machines?

Romo

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that.

My clones take 30-40 seconds, how do you thin provision? Using virt-sparsify on an image?

No, qcow2 is thin by default. But all of my templates are RHEL systems. So the OS doesn't use hardly any space. Are you cloning Windows machines?

No, no windows

Romo

@stacksofplates said in KVM Snapshot/Backup Script:

I create the template, and run virt-sysprep on it. Then I can update the disk with virt-sysprep --update. It automatically spins up a temp VM that updates all of the packages in the disk. But if you do this, you need to run virt-sysprep --selinux-relabel so it relabels the disk on the next clone. If not, labels can get screwed up;

Is this is only available for RHEL guests or can it be used with other distros?

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that.

My clones take 30-40 seconds, how do you thin provision? Using virt-sparsify on an image?

No, qcow2 is thin by default. But all of my templates are RHEL systems. So the OS doesn't use hardly any space. Are you cloning Windows machines?

No, no windows

Hmm, I don't have anything special. Some 300G 10K SAS drives in RAID 10.

Here's a video I did for Dash:
Youtube Video

And another of a script I wrote that names the VM and spins up how many instances you tell it:
Youtube Video

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

I create the template, and run virt-sysprep on it. Then I can update the disk with virt-sysprep --update. It automatically spins up a temp VM that updates all of the packages in the disk. But if you do this, you need to run virt-sysprep --selinux-relabel so it relabels the disk on the next clone. If not, labels can get screwed up;

Is this is only available for RHEL guests or can it be used with other distros?

You should be able to sysprep Ubuntu also. Not sure about any others.

Romo

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that.

My clones take 30-40 seconds, how do you thin provision? Using virt-sparsify on an image?

No, qcow2 is thin by default. But all of my templates are RHEL systems. So the OS doesn't use hardly any space. Are you cloning Windows machines?

No, no windows

Hmm, I don't have anything special. Some 300G 10K SAS drives in RAID 10.

Here's a video I did for Dash:
Youtube Video

And another of a script I wrote that names the VM and spins up how many instances you tell it:
Youtube Video

I want that speed!! I am on 4 500GB 7200 SATA in RAID 10

stacksofplates

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

@stacksofplates said in KVM Snapshot/Backup Script:

@Romo said in KVM Snapshot/Backup Script:

Are you using external snapshots to thin provision any vms? Is there a performance hit on doing this?

No. I have a template that uses a qcow2 disk. It's only a 15GB disk, but since it's thin provisioned it's only around 1.5GB. I can clone it in about 1-2 seconds so I haven't bothered with doing externals for that.

My clones take 30-40 seconds, how do you thin provision? Using virt-sparsify on an image?

No, qcow2 is thin by default. But all of my templates are RHEL systems. So the OS doesn't use hardly any space. Are you cloning Windows machines?

No, no windows

Hmm, I don't have anything special. Some 300G 10K SAS drives in RAID 10.

Here's a video I did for Dash:
Youtube Video

And another of a script I wrote that names the VM and spins up how many instances you tell it:
Youtube Video

I want that speed!! I am on 4 500GB 7200 SATA in RAID 10

How big is your template?

2.0G -rw-------. 1 root root  16G Feb 13 03:37 template.qcow2

That's what I have.

stacksofplates

Also it's not virt-sysprep --update it's virt-customize --update. I didn't think that was right, so I just went back and looked.

I have a daily cron job that runs this

/bin/virt-customize --update --selinux-relabel -a /data/VMs/template.qcow2