Antony: /* Export Glance images out of Ceph */

2023-11-15T12:29:39Z

Export Glance images out of Ceph

Mariusz: Add some initial rados/rdb commands

2020-02-28T13:23:53Z

Add some initial rados/rdb commands

New page

=== List Ceph pools ===

<nowiki>
rados lspools
</nowiki>

=== List objects in a Ceph pool ===

<nowiki>
rados -p <your-pool> ls
</nowiki>

=== Remove an object from a Ceph pool ===

<nowiki>
rados -p <your-pool> rm <object-name>
</nowiki>

=== Copy an object in a pool ===

<nowiki>
rados -p <your-pool> cp <source-object> <target-object>
</nowiki>

When Nova uses Ceph as the backend, this command can be used to backup OpenStack instance disk files or to transfer disks from one instance to another without having to create a snapshot or to export the disk file out of Ceph and back in again.

Let's say we want to transfer disk of this instance to a different instance:

<nowiki>
$ openstack server list
+--------------------------------------+-------+--------+--------------------------+--------+---------+
| ID | Name | Status | Networks | Image | Flavor |
+--------------------------------------+-------+--------+--------------------------+--------+---------+
| 1b2538e1-5f8e-4401-a69f-5c3c0ce41d72 | demo1 | ACTIVE | internal=192.168.100.147 | cirros | m1.tiny |
+--------------------------------------+-------+--------+--------------------------+--------+---------+
</nowiki>
Firstly, launch an instance that uses the same flavour (the base image doesn't matter) -- this will be the receiver of the disk. Then stop both instances to avoid corrupting data on the disk during the transfer:

<nowiki>
$ openstack server list
+--------------------------------------+-------+--------+--------------------------+--------+---------+
| ID | Name | Status | Networks | Image | Flavor |
+--------------------------------------+-------+--------+--------------------------+--------+---------+
| c5f4e1cd-0c3b-4388-9017-dab18072cb2b | demo2 | ACTIVE | internal=192.168.100.100 | cirros | m1.tiny |
| 1b2538e1-5f8e-4401-a69f-5c3c0ce41d72 | demo1 | ACTIVE | internal=192.168.100.147 | cirros | m1.tiny |
+--------------------------------------+-------+--------+--------------------------+--------+---------+
$ openstack server stop demo1
$ openstack server stop demo2
</nowiki>
Then replace the disk file of the new instance with the old disk in Ceph:

<span style="color:red">BE EXTRA CAREFUL AND MAKE SURE YOU'RE REMOVING THE CORRECT DISK IMAGE!!!</span>
<nowiki>
# rados -p vms ls | grep c5f4e1cd-0c3b-4388-9017-dab18072cb2b
rbd_id.c5f4e1cd-0c3b-4388-9017-dab18072cb2b_disk
# rados -p vms rm rbd_id.c5f4e1cd-0c3b-4388-9017-dab18072cb2b_disk
# rados -p vms ls | grep 1b2538e1-5f8e-4401-a69f-5c3c0ce41d72
rbd_id.1b2538e1-5f8e-4401-a69f-5c3c0ce41d72_disk
# rados -p vms cp rbd_id.1b2538e1-5f8e-4401-a69f-5c3c0ce41d72_disk rbd_id.c5f4e1cd-0c3b-4388-9017-dab18072cb2b_disk
</nowiki>

Turn the newer instance on and it will have all the files that the original instance had on its disk.

=== Export Glance images out of Ceph ===

<nowiki>
rbd export --pool=images <image-uuid> <outpu-file.img>
</nowiki>
This will also work for exporting disk images of instances -- simply use <code>--pool=vms</code> instead and <code><your-instance-uuid>_disk</code> as the source image.

=== Resources ===

# https://docs.ceph.com/docs/master/man/8/rados/
# http://www.sebastien-han.fr/blog/2012/07/03/download-a-glance-image-from-rbd/

@@ Line 64: / Line 64: @@
 === Export Glance images out of Ceph ===
+==== To a file on the local machine ====
   <nowiki>
 rbd export --pool=images <image-uuid> <outpu-file.img>
@@ Line 70: / Line 70: @@
 This will also work for exporting disk images of instances -- simply use <code>--pool=vms</code> instead and <code><your-instance-uuid>_disk</code> as the source image.
 === Resources ===

Ceph:Operating:Useful RADOS commands - Revision history

Antony: /* Export Glance images out of Ceph */

Mariusz: Add some initial rados/rdb commands