Ubuntu/Debian Add LZ4-Compressed Initramfs Support, Will Auto Decide LZ4/XZ Choice

Back in March was the discussion about Ubuntu 18.10 considering an LZ4-compressed kernel image (initamfs) by default while now action has been taken on this support and coming up with a new default.

With the latest Ubuntu and Debian packages, compressing the initramfs using LZ4 is now supported. Ubuntu up to this point has been using the basic Gzip compression support. The benefit to using an LZ4-compressed image is much quicker decompression than alternative algorithms but it does mean a slightly larger file size.

So while LZ4 is now supported, the plan by Ubuntu developers is to use some automatic determination which compression choice is back for a particular system. On systems having a small boot partition or embedded systems, the "auto" default would use XZ compression on these small systems due to it yielding the greatest file compression ratio. But if there aren't boot partition constraints, LZ4 would be used since it's the fastest option.

The change of the defaults should hopefully be good to go for the October release of Ubuntu 18.10.