Recovering from a broken guest

Discussions about using Windows guests in VirtualBox.
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BCosell
Posts: 73
Joined: 12. Jul 2017, 20:27

Recovering from a broken guest

Post by BCosell »

VB 6.1.40 on win10host/win10guest: I often use my guest system as a testbed for trying new stuff. The other day I did something in my guest that utterly screwed it up. Is there a way to get back to the pre-screwed-up state without deleting the whole guest and rebuilding it?

I noticed that the .vdi file is modified when I start up the guest but it doesn't seem to be modified as I use it during the day, so I was wondering if it is possible to safely "nuke" the running guest and get back to the guest as it was before I last started it and messed it up.
mpack
Site Moderator
Posts: 39156
Joined: 4. Sep 2008, 17:09
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Mostly XP

Re: Recovering from a broken guest

Post by mpack »

BCosell wrote:VB 6.1.40 on win10host/win10guest: I often use my guest system as a testbed for trying new stuff. The other day I did something in my guest that utterly screwed it up. Is there a way to get back to the pre-screwed-up state without deleting the whole guest and rebuilding it?
Yes, it's trivially easy to recover from that kind of failure. You just copy your most recent backup of this VM back to the host PC.

If you don't make backups then no, you can't recover from a disaster without a lot of work.

It's possible that you can undo the mistake you made inside the guest. That would depend on what the error was.
BCosell
Posts: 73
Joined: 12. Jul 2017, 20:27

Re: Recovering from a broken guest

Post by BCosell »

Ah , thanks. I was afraid of that. I assume when you say restore, you mean both the .vbox file and the .vdi file. I'll have to see about backing it up. I rarely make "permanent" changes to the guest system, so I'll be careful to back it up when I change something [e.g., install a new program].
mpack
Site Moderator
Posts: 39156
Joined: 4. Sep 2008, 17:09
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Mostly XP

Re: Recovering from a broken guest

Post by mpack »

BCosell wrote:I assume when you say restore, you mean both the .vbox file and the .vdi file.
You backup and restore the VM, i.e. the entire contents of the VM folder. Not just a couple of the files. The vdi file(s) will account for almost all of it, so there's no reason to skip the rest - the smaller files contain important info too, such as the hardware id's needed to keep your guest software activated.
BCosell
Posts: 73
Joined: 12. Jul 2017, 20:27

Re: Recovering from a broken guest

Post by BCosell »

I just checked and the only things in my VB folder are the .vdi and .vbox files and an empty "snapshot" directory and a log directory. I guess I can add the logs to the files I back up..
mpack
Site Moderator
Posts: 39156
Joined: 4. Sep 2008, 17:09
Primary OS: MS Windows 10
VBox Version: PUEL
Guest OSses: Mostly XP

Re: Recovering from a broken guest

Post by mpack »

Do NOT back up a file at a time, back up the entire folder. Don't try to parse the contents. Backing up specific files simply invites new files to be missed, possibly resulting in a useless backup.
BCosell
Posts: 73
Joined: 12. Jul 2017, 20:27

Re: Recovering from a broken guest

Post by BCosell »

Thanks for all the advice. I now, as recommended, back up the entire directory. If anyone is interested, I've written a pair of Perl programs that save and restore VMs. It makes two entries in the backup folder
vm.PNG
vm.PNG (4.26 KiB) Viewed 1089 times
and the text file has a comment describing what/why the backup represents [so if you need to restore you can figure out which backups are which]. Let me know if you'd like a copy of the programs
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