If you don't have 4.13.0-21 still installed, you can download it from: https://launchpad.net/~canonical-kernel-team/+archive/ubuntu/ppa/+build/13870500
If you don't have 4.13.0-21 still installed, you can download it from: /launchpad. net/~canonical- kernel- team/+archive/ ubuntu/ ppa/+build/ 13870500
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