How to capture kernel boot output

Are you using Lish? That will show you what's happening as it boots. You can access Lish via Linode Manager -> -> Remote Access, use either the AJAX terminal, or execute the ssh command listed for Lish. From your Linode Manager, execute a reboot and watch your Lish terminal. You can find instructions for using Lish right in the Linode Library.

Yes, lish and this is what I can look at :roll:

[screen is terminating]

Why use screen when you can use Lish?

lish is using screen

Yes, but it's not running screen on your Linode, it's running screen outside of your Linode. Screen should only terminate if it's on your Linode and there's some sort of problem.

I found logview command, but it shows only last 100 lines.

How would one collect all output?

I am pretty sure kernel panic can be considered a problem.

screen session is terminated and all output is gone.

I can collect only last 100 lines using lish logview command.

I would like to collect all output.