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• LXD sits on top of LXC and uses a higher level set of commands
• REST API to orchestrates containers locally and remotely
• Allows moving and copying between hosts
• Takes advantage of advanced file systems (in particular ZFS)
• Improves on security specifically running as unprivileged hence root inside container does not get root on host

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Setup 

Don't mix. Either On your host system, either install LXC or install LXD which adds LXC Underlying Components. I found installing just LXC results in components which are different than those packaged with  LXD. Though LXD setups an LXC subsystem, If found that the packages are different.

A key feature of virtualization technology is taking snapshots. With traditional file systems, this is expensive in terms of storage and speed. Next generation ZFS solves many of theses problems and it is recommended by Ubuntu to install and use with LXD,

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