EBC Exercise 22 Updating the Kernel

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thumb‎ Embedded Linux Class by Mark A. Yoder


The kernel can be easily updated with one command. Here's how to do it.

Checking kernel version and Installing

First see which version of the kernel you are running. 

bone$ uname -a
Linux beaglebone 5.10.168-ti-r62 #1bullseye SMP PREEMPT Tue May 23 20:15:00 UTC 2023 armv7l GNU/Linux
GNU/Linux

The 5.10.168-ti-r62 string is the kernel version.

To update to the current kernel, ensure that your Bone is on the Internet and then run the following commands: 

bone$ apt-cache pkgnames | grep linux-image | sort | less
...
linux-image-5.10.162-ti-r59
linux-image-5.10.162-ti-rt-r56
linux-image-5.10.162-ti-rt-r57
linux-image-5.10.162-ti-rt-r58
linux-image-5.10.162-ti-rt-r59
linux-image-5.10.168-armv7-lpae-x71
linux-image-5.10.168-armv7-rt-x71
linux-image-5.10.168-armv7-x71
linux-image-5.10.168-bone71
linux-image-5.10.168-bone-rt-r71
linux-image-5.10.168-ti-r60
linux-image-5.10.168-ti-r61
linux-image-5.10.168-ti-r62
linux-image-5.10.168-ti-rt-r60
linux-image-5.10.168-ti-rt-r61
linux-image-5.10.168-ti-rt-r62
...

bone$ sudo apt install linux-image-5.10.162-ti-r59
bone$ ```sudo reboot```

bone$ ```uname -a```
Linux beaglebone 5.10.162-ti-r59 #1 SMP PREEMPT Wed Nov 19 21:11:08 UTC 2014 armv7l
GNU/Linux

The first command lists the versions of the kernel that are available. The second command installs one. After you have rebooted, the new kernel will be running.

If the current kernel is doing its job adequately, you probably don’t need to update, but sometimes a new software package requires a more up-to-date kernel. Fortunately, precompiled kernels are available and ready to download.

Seeing which kernels are installed

You can have multiple kernels install at the same time. They are saved in /boot 

bone$ cd /boot
bone$ ls 
config-5.10.168-ti-r62      initrd.img-5.10.168-ti-r63  uboot                    vmlinuz-5.10.168-ti-r63
config-5.10.168-ti-r63      SOC.sh                      uEnv.txt
dtbs                        System.map-5.10.168-ti-r62  uEnv.txt.orig
initrd.img-5.10.168-ti-r62  System.map-5.10.168-ti-r63  vmlinuz-5.10.168-ti-r62

Here I have two kernel versions installed. On the Bone (Not the Play) the file uEnv.txt tells which kernel to use on the next reboot. Here are the first few lines: 

Line
  1 #Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
  2 
  3 # uname_r=4.14.108-ti-r137
  4 uname_r=4.19.94-ti-r50
  5 # uname_r=5.4.52-ti-r17
  6 #uuid=

Lines 3-5 list the various kernels, and the uncommented one on line 4 is the one that will be used next time. You will have to add your own uname's. Get the names from the files in /boot. Be careful, if you mistype the name your Bone won't boot.

Recovering

If you do mistype that name and your Bone won't boot. Do the following

  • Turn the Bone's power off.
  • Remove the SD card.
  • Put SD card is your host computer.
  • cd to /boot on the card.
bone$ cd /media/$USER/rootfs/boot
  • Use your favorite editor to edit uEnv.txt and correct it.



thumb‎ Embedded Linux Class by Mark A. Yoder

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