I've today had two machines kill my X session during dist-upgrade, and it happened during libc6 postinst. Dmesg shows that systemd got somehow started during the earlier phase of the upgrade. X logs show a failure with "(EE) Cannot establish any listening sockets" etc..
Adam can fill in the more detailed analysis of what's happening there.. but I think it should be fairly easy to reproduce by installing vivid from an earlier image and dist-upgrading to current, if needed.
I've today had two machines kill my X session during dist-upgrade, and it happened during libc6 postinst. Dmesg shows that systemd got somehow started during the earlier phase of the upgrade. X logs show a failure with "(EE) Cannot establish any listening sockets" etc..
Adam can fill in the more detailed analysis of what's happening there.. but I think it should be fairly easy to reproduce by installing vivid from an earlier image and dist-upgrading to current, if needed.