$ sudo rpi-update
 *** Raspberry Pi firmware updater by Hexxeh, enhanced by AndrewS and Dom
 *** Performing self-update
 *** Relaunching after update
 *** Raspberry Pi firmware updater by Hexxeh, enhanced by AndrewS and Dom
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This update bumps to rpi-4.4.y linux tree
Be aware there could be compatibility issues with some drivers
Discussion here:
https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=144087
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 *** Downloading specific firmware revision (this will take a few minutes)
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   168    0   168    0     0     44      0 --:--:--  0:00:03 --:--:--    44
100 50.6M  100 50.6M    0     0   128k      0  0:06:42  0:06:42 --:--:-- 47287
 *** Updating firmware
 *** Updating kernel modules
 *** depmod 4.4.14-v7+
 *** depmod 4.4.14+
 *** Updating VideoCore libraries
 *** Using HardFP libraries
 *** Updating SDK
 *** Running ldconfig
 *** Storing current firmware revision
 *** Deleting downloaded files
 *** Syncing changes to disk
 *** If no errors appeared, your firmware was successfully updated to f88187f2bcdb05303b74315bdf984fd25523a0f5
 *** A reboot is needed to activate the new firmware