No kdump is created

[Sebastian Andersson]

After creating a test crash (echo c > /proc/sysrq-trigger), the Ubuntu splash screen is shown for around 20 seconds, with the dots being filled and cleared, then the system restarts into, what I assume is, the configured kdump-initrd-image and gives me a busybox shell.
The system's root is not mounted, its block-device is not available under /dev.

Rebooting from there back to the normal system shows no dumped kernel under the configured /var/crash directory. /var/crash is part of the root fs, an ext4 mounted from /dev/nvme0n1p3

Expected behaviour:
echo c > /proc/sysrq-trigger
should give a kdump file in /var/crash

Actual behavior:
no file i /var/crash, a busybox shell in the kexec:ed kernel.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: kexec-tools 1:2.0.10-1ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-57.78-generic 4.4.35
Uname: Linux 4.4.0-57-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.4
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Jan 5 21:38:57 2017
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-01-03 (2 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
SourcePackage: kexec-tools
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.default.grub.d.kexec-tools.cfg: GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT crashkernel=384M-:256M"
mtime.conffile..etc.default.grub.d.kexec-tools.cfg: 2017-01-05T18:09:40.998631

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.