Chapter 7. Booting from cinder volumes
This section contains information on creating and connecting volumes created in OpenStack Block Storage (cinder) to bare metal instances created with OpenStack Bare Metal (ironic).
7.1. Cinder volume boot for bare metal nodes
You can boot bare metal nodes from a block storage device that is stored in OpenStack Block Storage (cinder). OpenStack Bare Metal (ironic) connects bare metal nodes to volumes through an iSCSI interface.
Ironic enables this feature during the overcloud deployment. However, consider the following conditions prior to deployment:
-
The overcloud requires the cinder iSCSI backend to be enabled. Set the
CinderEnableIscsiBackend
heat parameter totrue
during overcloud deployment. - You cannot use the cinder volume boot feature with a Red Hat Ceph Storage backend.
-
You must set the
rd.iscsi.firmware=1
kernel parameter on the boot disk.
7.2. Configuring nodes for cinder volume boot
You must configure certain options for each bare metal node to successfully boot from a cinder volume.
Procedure
-
Log in to the undercloud as the
stack
user. Source the overcloud credentials:
$ source ~/overcloudrc
Set the
iscsi_boot
capability totrue
and thestorage-interface
tocinder
for the selected node:$ openstack baremetal node set --property capabilities=iscsi_boot:true --storage-interface cinder <NODEID>
Replace `<NODEID> with the ID of the chosen node.
Create an iSCSI connector for the node:
$ openstack baremetal volume connector create --node <NODEID> --type iqn --connector-id iqn.2010-10.org.openstack.node<NUM>
The connector ID for each node must be unique. In the example, the connector is
iqn.2010-10.org.openstack.node<NUM>
where<NUM>
is an incremented number for each node.
7.3. Configuring iSCSI kernel parameters on the boot disk
You must enable the iSCSI booting in the kernel on the image. To accomplish this, mount the QCOW2 image and enable iSCSI components on the image.
Prerequisites
Download a Red Hat Enterprise Linux QCOW2 image and copy it to the
/home/stack/
directory on the undercloud. You can download Red Hat Enterprise Linux KVM images in QCOW2 format from the following pages:
Procedure
-
Log in to the undercloud as the
stack
user. Mount the QCOW2 image and access it as the
root
user:Load the
nbd
kernel module:$ sudo modprobe nbd
Connect the QCOW image as
/dev/nbd0
:$ sudo qemu-nbd --connect=/dev/nbd0 <IMAGE>
Check the partitions on the NBD:
$ sudo fdisk /dev/nbd0 -l
New Red Hat Enterprise Linux QCOW2 images contain only one partition, which is usually named
/dev/nbd0p1
on the NBD.Create a mount point for the image:
mkdir /tmp/mountpoint
Mount the image:
sudo mount /dev/nbd0p1 /tmp/mountpoint/
Mount your
dev
directory so that the image has access to device information on the host:sudo mount -o bind /dev /tmp/mountpoint/dev
Change the root directory to the mount point:
sudo chroot /tmp/mountpoint /bin/bash
Configure iSCSI on the image:
NoteSome commands in this step might report the following error:
lscpu: cannot open /proc/cpuinfo: No such file or directory
This error is not critical and you can ignore the error.
Move the
resolv.conf
file to a temporary location:# mv /etc/resolv.conf /etc/resolv.conf.bak
Create a temporary
resolv.conf
file to resolve DNS requests for the Red Hat Content Delivery Network. This example uses8.8.8.8
for the nameserver:# echo "nameserver 8.8.8.8" > /etc/resolv.conf
Register the mounted image to the Red Hat Content Delivery Network:
# subscription-manager register
Enter your username and password when the command prompts you.
Attach a subscription that contains Red Hat Enterprise Linux:
# subscription-manager list --all --available # subscription-manager attach --pool <POOLID>
Substitute
<POOLID>
with the pool ID of the subscription.Disable the default repositories:
# subscription-manager repos --disable "*"
Enable the Red Hat Enterprise Linux repository:
Red Hat Enterprise Linux 7:
# subscription-manager repos --enable "rhel-7-server-rpms"
Red Hat Enterprise Linux 8:
# subscription-manager repos --enable "rhel-8-for-x86_64-baseos-rpms"
Install the
iscsi-initiator-utils
package:# yum install -y iscsi-initiator-utils
Unregister the mounted image:
# subscription-manager unregister
Restore the original
resolv.conf
file:# mv /etc/resolv.conf.bak /etc/resolv.conf
Check the kernel version on the mounted image:
# rpm -qa kernel
For example, if the output is
kernel-3.10.0-1062.el7.x86_64
, the kernel version is3.10.0-1062.el7.x86_64
. Note this kernel version for the next step.NoteNew Red Hat Enterprise Linux QCOW2 image have only one kernel version installed. If more than one kernel version is installed, use the latest one.
Add the
network
andiscsi
dracut modules to the initramfs image:# dracut --force --add "network iscsi" /boot/initramfs-<KERNELVERSION>.img <KERNELVERSION>
Replace
<KERNELVERSION>
with the version you obtained fromrpm -qa kernel
. The following example uses3.10.0-1062.el7.x86_64
as the kernel version:# dracut --force --add "network iscsi" /boot/initramfs-3.10.0-1062.el7.x86_64.img 3.10.0-1062.el7.x86_64
Edit the
/etc/default/grub
configuration file and addrd.iscsi.firmware=1
to theGRUB_CMDLINE_LINUX
parameter:# vi /etc/default/grub
The following example shows the
GRUB_CMDLINE_LINUX
parameter with the addedrd.iscsi.firmware=1
kernel argument:GRUB_CMDLINE_LINUX="console=tty0 crashkernel=auto console=ttyS0,115200n8 no_timer_check net.ifnames=0 rd.iscsi.firmware=1"
Save these changes.
NoteDo not rebuild the
grub
menu configuration at this step. A later step in this procedure rebuilds thegrub
menu as a temporary virtual machine.Exit from the mounted image back to your host operating system:
# exit
Unmount the image:
Unmount the
dev
directory from the temporary mount point:$ sudo umount /tmp/mountpoint/dev
Unmount the image from the mount point:
$ sudo umount /tmp/mountpoint
Disconnect the QCOW2 image from
/dev/nbd0/
:$ sudo qemu-nbd --disconnect /dev/nbd0
Rebuild the
grub
menu configuration on the image:Install the
libguestfs-tools
package:$ sudo yum -y install libguestfs-tools
ImportantIf you install the
libguestfs-tools
package on the undercloud, disableiscsid.socket
to avoid port conflicts with thetripleo_iscsid
service on the undercloud:$ sudo systemctl disable --now iscsid.socket
Set the
libguestfs
backend to use QEMU directly:$ export LIBGUESTFS_BACKEND=direct
Update the grub configuration on the image:
$ guestfish -a <IMAGE> -m /dev/sda1 sh "/sbin/grub2-mkconfig -o /boot/grub2/grub.cfg"
7.4. Creating and using a boot volume in cinder
You must upload the iSCSI-enabled image to OpenStack Image Storage (glance) and create the boot volume in OpenStack Block Storage (cinder).
Procedure
-
Log in to the undercloud as the
stack
user. Upload the iSCSI-enabled image to glance:
$ openstack image create --disk-format qcow2 --container-format bare --file rhel-server-7.7-x86_64-kvm.qcow2 rhel-server-7.7-iscsi
Create a volume from the image:
$ openstack volume create --size 10 --image rhel-server-7.7-iscsi --bootable rhel-test-volume
Create a bare metal instance that uses the boot volume in cinder:
$ openstack server create --flavor baremetal --volume rhel-test-volume --key default rhel-test