** Description changed: - Description will be saved for further SRU template, the details of the - issue will be exposed in comments + [Impact] + * Considering a setup of a encrypted rootfs on top of md RAID1 device, Ubuntu is currently unable to decrypt the rootfs if the array gets degraded, like for example if one of the array members gets removed. + + * The problem has 2 main aspects: first, cryptsetup initramfs script + attempts to decrypt the array only in the local-top boot stage, and in + case it fails, it gives-up and show user a shell (boot is aborted). + + * Second, mdadm initramfs script that assembles degraded arrays executes + later on boot, in the local-block stage. So, in a stacked setup of + encrypted root on top of RAID, if the RAID is degraded, cryptsetup fails + early in the boot, preventing mdadm to assemble the degraded array. + + [Proposed solution] + * The solution hereby proposed has 3 components: first, cryptsetup script is modified to allow a gentle failure on local-top stage, then it retries for a while in a later stage (local-block). This gives time to other initramfs scripts to run, like mdadm in local-block stage. + + * Second, mdadm script was adjusted - currently, it retries for a while + to assemble the arrays in a non-degraded mode, by waiting for udev to + discover the missing devices. After some time, it gives-up and assembles + all arrays as degraded. The adjust we made was only to reduce this + number of attempts and fallback a bit faster to degraded array assembly. + + * Third, there's a difference in Ubuntu initramfs-tools compared to + Debian's : in Ubuntu, we rely on wait-for-root, a binary meant to speed- + up the boot process. Problem is that currently this approach prevents + local-block scripts to run more than once (thus retrying mechanisms will + fail). Our proposed solution changes initramfs-tools to allow some + looping in local-block stage (as Debian), but still relying on wait-for- + root. Also, we increased a bit the default rootdelay from 30 seconds to + 60 seconds. + + + [Test case] + * Install Ubuntu in a Virtual Machine with 2 disks. Use the installer to create a RAID1 volume and an encrypted root on top of it. + + * Boot the VM, and use "sgdisk"/"wipefs" to erase the partition table + from one of the RAID members. Reboot and it will fail to mount rootfs + and continue boot process. + + + [Regression potential] + + * There are potential for regressions, since this is a change in 3 boot + components. The patches were designed in a way to keep the regular case + working, it changes the failure case which is not currently working + anyway. + + * A potential issue in the initramfs-tools change is a bad script in + local-block, lacking a good "halt" mechanism, to induce a boot loop + condition. This problem would be exposed by the hereby proposed + modification.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1879980 Title: Fail to boot with LUKS on top of RAID1 if the array is broken/degraded To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cryptsetup/+bug/1879980/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
