I experienced the same issue on Mint 17.1 Cinnamon 64 after a power failure during an update run. Your methodology of booting a live cd, mounting the partitions, chroot, and complete the updates worked for me and I was able to recover my system.
I posted my experience on the Mint forums here:- http://forums.linuxmint.com/viewtopic.php?f=46&t=196408
I experienced the same issue on Mint 17.1 Cinnamon 64 after a power failure during an update run.
Your methodology of booting a live cd, mounting the partitions, chroot, and complete the updates worked for me and I was able to recover my system.
I posted my experience on the Mint forums here:- forums. linuxmint. com/viewtopic. php?f=46& t=196408
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