New Raspbian Kernel After Reboot?

[MacsandaPi]

My B+ was running kernel version 3.12.35+ until I rebooted last night; now I see the version is 3.18.5+. Are the kernels updated and downloaded automatically to connected computers? I thought it was necessary to run the sudo update/upgrade commands to get updated kernels.

Thanks in advance for clarifying this point.

[AndyD]

No automatic kernel download. You have to use apt-get update and apt-get upgrade (rpi-update will also update the kernel). Is it possible that you have upgrade at another time and only rebooted recently? You won't see the new kernel version until you reboot.