Ubuntu Core 18 can not find init


#1

I have created a Core 18 image for our PC, here the json file:

{
“type”: “model”,
“series”: “16”,
“model”: “stealth-demo”,
“architecture”: “amd64”,
“base”: “core18”,
“kernel”: “pc-kernel=18”,
“gadget”: “pc=18”,
“authority-id”: “xhmfBp3zLFaGnZWriwXk7LAIesOMfk2T”,
“brand-id”: “xhmfBp3zLFaGnZWriwXk7LAIesOMfk2T”,
“timestamp”: “2019-04-11T07:58:27+00:00”,
“required-snaps”: [“ros-foundation-kinetic-canvas” ]
}

I have no problem, booting this image on VirtualBox or Multipass.

When I install it on the real computer, I use the dual USB technique, I boot from USB using a 18.04 install USB boot, choose Try Ubuntu and then use a terminal
to dd the image onto the disk.

The image then boot fine, I can go thru the first boot initialization sequence, no problem.
If I reboot the machine, the second reboot works most of the time but after that each time I reboot, the image fails to boot and can not find init.!

Here the error image:

I’m a bit lost on what is happening here.


#2

That seems odd. @ogra, @ondra, ever seen anything like this?


#3

sure … half a page above it likely says “writable partition not found” or something along these lines …

first step should be to take a look at /dev/disk/by-label if there is a “writable” (from the spawned initramfs shell)


#4

yes there is a partition /dev/disk/by-label/writable

ls -l gives me this:
lrwxrwxrwx . 1 10 writable -> …/…/sdb3
lrwxrwxrwx . 1 . 10 writable -> …/…/sda2

So there is a second disk but we are not using it (yet) and the system should be all on sda, I’m wondering why sdB is being used.


#5

Update, since Core18 was trying to access sdb, I disable sdb in the Bios as a test. Now it boots every single time.
So the next question: is there anything special I should do to build an Core18 image that can handle two physical disks?

Thanks for helping, it’s now working enough we can start testing our robot.


#6

don’t give the second disc a partition with a writable label.


#7

I don’t think I did that but I might have done some test on this disk before (hence the “writable” label might be there). I will do a full reformat and try again.


#8

@kyrofa @rvincent25 I have seen this quite a few times.
But’s let’s try if this is same issue, was this second boot of the device? Are you super sure first boot completed successfully?
I see this when following happens:

  • first boot fails, so snapd uninstalls core and kernel snaps, which means it removes symboling links in /var/lib/snapd/snaps pointing to not yet installed snaps in /var/lib/snapd/seed/snaps.
  • when device tries to boot second time, not initrd is looking for core snap at /var/lib/snapd/snaps
    but it ain’t there because snapd removed symlink because of failed boot

Your screenshot points to this because I can see that initrd is failing to see core and kernel snap…


#9

@ondra, yes that was the problem. Our computer came pre-installed with ubuntu on the other partition.
Reformatting the other disks made the problem go away. Issue resolved.