Rescue mode but no rescuer
I thought I would share my experience after a blue screen stopped my Oracle VirtualBox VM running Home Assistant from running.
I have some Linux command line experience so I thought I would get to know Home Assistant by trying to fix it with a little help from Google and ChatGPT.
The first sign of trouble was this depressing You are in rescue mode
Typing reboot at the # prompt a couple of times did not resolve the issue.
I also tried using Slot B rather than Slot A in that GNU GRUB start-up screen. At least this time I saw some containerd errors but then a blank screen and a Slot B rescue shell followed.
Containerd snookerd
The journalctl -xb command revealed lots of scary error messages linked to containerd so I resigned myself to trying to rebuild HA from scratch.
I downloaded the VDI from https://www.home-assistant.io/installation/windows/ and extracted the VDI file to the same folder as the VM. Rather than build up the VM itself from scratch, I backed up the folder and then went to the corrupt VM's settings - storage - hit add attachment and then Add (disk image file) and selected the new VDI file.
This was enough to get me to a pristine set-up and I was ready to restore a backup.
Backed up
I had been careful to configure a daily backup with at least 7 backup copies. And...of course, these were on the VDI disk that had the corrupted HA. 
Then I thought "how hard could it be to get hold of that file. The VDI's just a file system after all".
It would be hard.
The good news is that VDI files can be read by 7-Zip and what I saw looked promising: a compressed file of the form {466....59}.img.
But when I tried to extract the file I got and error Unsupported compression method
Thankfully I "discovered" 
that there is a tool in VirtualBox that allows the extraction of this image file so I ran the command:
VBoxManage clonemedium disk {466...59}.vdi olddisk.img --format RAW
This is usually found in C:\Program Files\Oracle\VirtualBox
So I finally had a .img file that, in theory, could be mounted in Linux. I eagerly spun up a wsl (Windows Subsystem for Linux) session, created a /mnt/tmp folder and did a
mount /path/to/olddisk.img /mnt/tmp
It worked and I was able to rummage around the old disk for the backup files.
cd /mnt/tmp; ls -l
This revealed folders such as supervisor and logs.
Emergency kit emergency
I discovered that the files were kept in the supervisor folder under backup:
cd supervisor/backup; ls -lt
So all I had to do was get that tar file onto my file system with a quick copy.
cp Automatic....tar /path/to/local/folder
That was it. Now all I had to do was to go to Upload backup and select the tar file for the backup file and that would be it. But no - I had to enter an encryption key protecting the tar file backup.
It was at this point I realised that there was an encryption key somewhere on my filesystem as part of the "Emergency kit" and I could not recall what file name I had used 
. Surely it was stored on the old disk? The answer was yes 
- in the supervisor/homeassistant/.storage/backup file.
grep password backup
The response is of the form "password": "xxxx-....-xxxx"
I was now able to restore the backup. And a few minutes later...success:
Lessons Learnt (promise)
I hope that this is been helpful because I struggled to find this information in one place. Here are the lessons I have learnt.
- Backup on external media or the cloud. HA supports Samba and you can access the backup directory by mounting it. A scheduled task, for example, can be used to copy the backups somewhere safe.
- Remember where you put your emergency kit.
- Consider taking regular snapshots of your VDI file if your hard disk has enough space.
- Read the rules regarding posting for new users. Most of my lovely embedded images had to be removed. At least emojis are allowed.
