boot2docker fails if the vbox vm has saved state?

[SvenDowideit]

moby/moby#7048 (comment)

[md5]

I've seen this happen when VirtualBox forces the VM to shut down due to low power.

[nathanleclaire]

I've run into this issue before and solved it with the manual discarding of saved state workaround, but I assumed it was fixed now.

My current:

Boot2Docker-cli version: v1.3.1
Git commit: 57ccdb8

[nathanleclaire]

This is still happening for me in boot2docker v1.4.0.

[tianon]

Do we have an easy way to reproduce, and much, much more importantly, a good way to programmatically detect a broken save state that needs to be discarded? We don't want to be discarding the VM's saved state willy-nilly, especially since "saved" is a totally valid state if your VM actually suspended properly.

[nathanleclaire]

Do we have an easy way to reproduce, and much, much more importantly, a good way to programmatically detect a broken save state that needs to be discarded? We don't want to be discarding the VM's saved state willy-nilly, especially since "saved" is a totally valid state if your VM actually suspended properly.

Agreed- I'll keep an eye out.

I've seen this happen when VirtualBox forces the VM to shut down due to low power.

This seems like a very good hypothesis to me since I just plugged my computer in after it had run out of battery today. Unfortunately I didn't think to boot2docker up -v to get more detailed debugging output before discarding the saved state. Odd as it sounds we might be able to try letting a laptop run out of power to reproduce.

[nathanleclaire]

@tianon @SvenDowideit What do you think of this approach:

Create a file (~/.boot2docker/saved_state_is_legit? :) ) to indicate that the boot2docker VM's saved state is "legitimate" any time that we save the state with boot2docker-cli (it will later be removed when boot2docker up runs). On boot2docker up, we discard the saved state if that file is not present.

That way, if a process outside of our control shuts down the VM with saved state (see https://forums.virtualbox.org/viewtopic.php?f=1&t=56109 and many other forum posts: apparently this is not uncommon) the file will not be there and we can safely discard the saved state. Then boot2docker up will work as normal and user will not have to Google around for the issue etc.

I know it is hacky but I cannot find any elegant way to query VBox or the OS to find out if the VM was shut down in "low power conditions" (or whatever else might be causing this issue).

[SvenDowideit]

/me imagines the following sequence....

• boot2docker up
• boot2docker suspend (making that file)
• reboot computer
• user does unrelated stuff in vbox
• so user resumes the b2d-vm from vbox UI, bypassing the removal of that file
• user proceeds to run out of battery
• user restarts, and b2d fails with the confusion that file was supposed to avoid.

so - why not detect the problem, and tell the user what to do next?

[md5]

I actually had VirtualBox shut down my boot2docker VM last night due to the battery getting below 5%. I ran VBoxManage showvminfo boot2docker-vm --machinereadable | grep VMState and saw that VMState=saved. After plugging in to AC power, I ran boot2docker up -v and the VM started up without any problems.

When I saw this failure previously, the situation may have been more complicated than just a simple low battery scenario. I think what had actually happened was that I had closed my laptop to put it to sleep while it had more than 5% battery and it had dropped to below 5% while it was "sleeping". When I turned it back on and saw that my docker ps was failing, I tried boot2docker up and it failed. Unfortunately, I don't have any record of that failure and can't check what VMState was.

Regardless, I think a reasonable approach for boot2docker could be to offer to delete the VMStateFile in the case that it isn't able to restart from a saved state, using an appropriate warning message.

[nathanleclaire]

Interesting. Thanks for the information @md5 !