Manual data recovery

Goal

Downloading a snapshot of an instance
Repairing the filesystem and mount it to extract data

Prerequisites

You should be able to use simple heat templates, like shown in the first steps tutorial.
You know the basics of using the OpenStack CLI-Tools.
Environment variables are set, like shown in the API-Access-Tutorial.

Optional: temporary work environment

Click here to show details

Temporary work environment

For this tutorial, we need a Linux environment and the OpenStack client in the SysEleven cloud. If you do not have that yet, you can create it with the following commands:

wget https://raw.githubusercontent.com/syseleven/heat-examples/master/kickstart/kickstart.yaml
...
openstack stack create -t kickstart.yaml --parameter key_name=<ssh key name> <stack name> --wait
...

Now we need to connect to the created instance.

ssh syseleven@<server-ip>

The following commands need to be executed in the ssh session.

We also need the OpenStack credentials (openrc-file).
You can download the file here.

source openrc

Create and download a snapshot

To recover data from an existing instance, we have to create a snapshot first.

WARNING: Creating instance snapshots of your server will make it unresponsive for a period of time (depending on the disk size).

openstack server image create <server uuid> --name <snapshot name> --wait

We can download the snapshot now. This can take a while.

openstack image save --file snapshot.qcow2 <snapshot name>

We can access the snapshot's contents via nbd.

sudo apt-get install -y qemu-utils
sudo modprobe nbd
sudo qemu-nbd --connect /dev/nbd0 snapshot.qcow2

Let's list the partitions.

$ sudo fdisk -l /dev/nbd0
Disk /dev/nbd0: 50 GiB, 53687091200 bytes, 104857600 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x974bb19a

Device      Boot Start       End   Sectors Size Id Type
/dev/nbd0p1 *     2048 104857566 104855519  50G 83 Linux

To repair the filesystem, use fsck.

# Using the option -y, fsck will repair without asking.
sudo fsck -f /dev/nbd0p1
[...]

Now we can mount the filesystem.

sudo mount /dev/nbd0p1 /mnt/

Conclusion

Now the data is accessible on /mnt/.
If it's an ext filesystem you should have a look in /mnt/lost+found.