Booting to Dracut (I trusted ChatGPT)

Greg_E

Let's say you don't have the metadata backed up... Is there a way to boot from a rescue disk and save the metadata?

bvitnik

@Greg_E Theoretically yes. I've never been in such situation so I would have to learn, experiment and improvise along the way. If you can mount the file system of the host, you can find XAPI database in this location:

/var/lib/xcp/state.db

This is an XML formated file. I don't know if this is the same format as metadata backup (I think it's JSON instead). So you could possibly restore this file to proper location and restart the host but you would probably need to change some references in it, like UUIDs of local file systems on a freshly installed system. Other possibility is that the state file could be converted to metadata backup and imported but I'm not aware of there being any such conversion tool. It would have to be improvised.

There is always alot you can do. It just depends how deep you want to go, how complex you can go and how much time you can spare.

nuentes

@bvitnik I'm still unclear what metadata backs up. I suppose I don't need to know specifically, but I'm assuming it doesn't include initramfs and initrd? So a simple metadata restore would not resolve my issue, presumably?

I'm worried about doing a reinstall - I'm assuming that would wipe the disk (although I know sometimes that's not the case with Linux reinstalls). I would prefer to preserve my VMs if possible. If I'm expecting to need to wipe the disk, then I'm not 100% certain that I have backups of all of my VMs, so I'd like to clone the disk. I ran into some issues trying to run clonezilla the other night, so I might just pull the SSD and clone it to another SSD bit for bit with a disk cloning enclosure.

Just to point out - yes, my system has been offline for approaching a week now. But I've recently moved, so I have a lot of other things going on in life right now. I'd like to get it back online asap of course, but life keeps getting in the way. I feel that you are over-estimating how much I've done and mucked about. Anything I've actually performed is pretty full documented in this thread

Pilow

@nuentes I explored my pool metadata backups, and I see a "part.1" file, that is a big XML of all the configuration of the pool

so yeah I don't think there is something else in here like your OS parameters, only pool config.

I could be wrong, but it's all I can see in here

AtaxyaNetwork

@nuentes You can reinstall without wiping the SR. Just plug the ISO, it will ask you if you want a clean install or a reinstall

Pilow

@AtaxyaNetwork yeah but if he doesn't have metadata backups, he will have SRs full of disconnected VDIs ? and the need to recreate each VM ?

AtaxyaNetwork

If I was in your place, I would do:

Disconnect all USB used as SR
Reinstall XCP-ng
if you have only a few VMs, my option would be just to redeploy XOA, REATTACH the SR (not create, REATTACH, be careful, a create will wipe your disk)
- Recreate VMs, attach the VDI, boot from here
if you have to many VM, directly after deploying XOA restore your metadata backup, it should be repluging the SR and create PDB at least (but it's been a while since I didn't use the metadata)

In any case, backup everything, especially the VDI (.vhd). If you have the VDI, you can work around with the rest

bvitnik

@nuentes metadata in this context is just XAPI database. In other words, it only contains information about your VMs, SRs, networks, pools etc. It does not contain anything system level. It is not a backup of the host system.

As far as I know, but someone from Vates can confirm, metadata backup functionality in XO is based on XAPI pool-dump-database command:

xe pool-dump-database file-name=dump.xml

There is some info about it here:

https://docs.xenserver.com/en-us/xenserver/8/dr/backup.html

P.S. I guess metadata backup is also XML just like XAPI state file (database). I don't know why JSON came to my mind regarding metadata backup.

Pilow

@bvitnik said in Booting to Dracut (I trusted ChatGPT):

P.S. I guess metadata backup is also XML just like XAPI state file (database). I don't know why JSON came to my mind regarding metadata backup.

Reply

perhaps because of other thread discussing metadatabackup.list in audit log

there is actually a bug there where the metadata is not only checked to be audited, but also completly dumped in JSON format.

AtaxyaNetwork

(BTW you don't have any backup from XOA ? If you have backup, you can just register a new XOA, connect to you remote and restore everything, it will be much simpler)