Why Linode Ubuntu so slow in reboot?

Hello,
You might be able to diagnose this with the Lish console. Sometimes, when my own Linode's have taken a long time to reboot, I have used this to find that some services are taking their time stopping. Some servers and other programs will make every effort to gracefully shut down by no longer accepting connections, finishing any send/receive operations on open connections, then closing them before shutting down. Something similar may be happening for you, also.

Blake

Thanks tt isn't easy task though to change server settings

That depends on what server might be causing the delay in shutdown, if any.

It’s also worth noting if you’re triggering a reboot from within the Linode’s OS, it takes a little while for “Lassie” to notice and power it back on.

It can be a bit quicker if you trigger a reboot from within the Manager, which bypasses the need for the Lassie watchdog.