Open Stack

On 09-02-21 12:23:58, Sean Mooney wrote:
> On Tue, 2021-02-09 at 11:21 +0000, Arnaud Morin wrote:
> > Hey all,
> > 
> > From time to time we are facing an issue when puting instance in rescue
> > with the same image as the one the instance was booted.
> > 
> > E.G.
> > I booted an instance using Debian 10, disk are:
> > 
> > debian at testarnaud:~$ lsblk
> > NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
> > sr0     11:0    1  486K  0 rom  
> > vda    254:0    0   10G  0 disk 
> > └─vda1 254:1    0   10G  0 part /
> > debian at testarnaud:~$ cat /etc/fstab 
> > # /etc/fstab: static file system information.
> > UUID=5605171d-d590-46d5-85e2-60096b533a18	/	ext4
> > errors=remount-ro	0	1
> > 
> > 
> > 
> > I rescued the instance:
> > $ openstack server rescue --image bc73a901-6366-4a69-8ddc-00479b4d647f testarnaud
> > 
> > 
> > Then, back in the instance:
> > 
> > debian at testarnaud:~$ lsblk
> > NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
> > sr0     11:0    1  486K  0 rom  
> > vda    254:0    0    2G  0 disk 
> > └─vda1 254:1    0    2G  0 part 
> > vdb    254:16   0   10G  0 disk 
> > └─vdb1 254:17   0   10G  0 part /
> > 
> > 
> > 
> > Instance booted on /dev/vdb1 instead of /dev/vda1
> > 
> > Is there anything we can configure on nova side to avoid this
> > situation?
>
> in ussuri lee yarwood added
> https://specs.openstack.org/openstack/nova-specs/specs/ussuri/implemented/virt-rescue-stable-disk-devices.html
> to nova which i belive will resolve the issue
> 
> from ocata+ i think you can add hw_rescue_bus=usb to get a similar
> effect but from ussuri we cahgne the layout so thtat the rescue disk
> is always used. lee is that right?

Yeah that's correct, from Ussuri (21.0.0) with the libvirt driver the
instance should continue to show all disks connected as normal with the
rescue disk appended last and always used as the boot device.

In your case, switching the rescue bus should change the default boot
device type n-cpu tells libvirt to use working around your problem.
Another obvious thing you can try is just using a different image so the
two MBRs don't conflict?

Cheers,

-- 
Lee Yarwood                 A5D1 9385 88CB 7E5F BE64  6618 BCA6 6E33 F672 2D76
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