I have indeed tried unplugging/swapping connected USB peripherals and that never appeared to help. The only thing that worked reliably for me was pinning the old .67 kernel. Something changed after that and the one thing that did stand out is a huge increase in the initrd image size of later kernels.
Anyway, out of all the systems I run 16.04 on only two suffer from this issue and they are completely different beasts (one is a home brew server and the other is a dell optiplex workstation - they are also the only ones that run root on btrfs). I've updated the home brew system to 18.04 and it appears to no longer suffer from the issue but then again I don't reboot it very often either so who really knows. The Dell still requires me to hit 'e' and hang out in the grub editor for a period of time before continuing to boot reliably. It is very strange because manually adding sleep statements to the generated grub.cfg does not work. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1686837 Title: ubuntu fails to boot with btrfs root (unable to mount root) Status in linux package in Ubuntu: Expired Bug description: Hello, Failing to mount / as btrfs has been haunting btrfs users on ubuntu for some time. Coming and going with kernel updates. After I upgraded to 17.04, it seems that the problem is back. It seems that a non-clean umount reboot always leads to a non-bootable system. If I boot into rescue (selecting in grub, not a livecd), kernel can find the root partition. I can also boot normally if root=... kernel parameter is set with the device name (/dev/sda6) instead of UUID=xxxx. So, there might be a bug in kernel that does not allow linux to identify the boot partition using UUID in some circumstances (probably after a dirt reboot). Maybe other distros do some magic at initrd that cleans the btrfs problem because some, like opensuse, do uses btrfs as default root fs. Anyway, even ubuntu own rescue can boot normally. This is a tricky bug to debug as I get no logs written and no emergency shell. Just an ugly kernel error and a backstack. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1686837/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
