AL2023 how to switch kernel

Question

After login on one of our EC2/AL2023 instances I see this:
Updates Information Summary: available
    4 Security notice(s)
        4 Important Security notice(s)
Security: kernel-6.1.66-91.160.amzn2023.x86_64 is an installed security update
Security: kernel-6.1.55-75.123.amzn2023.x86_64 is the currently running version
How do I switch to the 6.1.66-91.160 kernel? I can't find any relevant documentation on this.
Live patching 6.1.66-91.160 works but I now want to start using it.

Answer

Reboot the instance and it will come back on the new kernel.

`sudo shutdown -r now`

Answer

For Live Kernel patching, you need to setup your instance with kpatch-dnf plugin. Take a look a this documentation. [1]

Once running, you can see the patches with the ` sudo kpatch list` command

[1] Kernel Live Patching on Amazon Linux 2023 - Enable Kernel Live Patching - https://docs.aws.amazon.com/linux/al2023/ug/live-patching.html#live-patching-enable

Answer

```
Security:Kernel-6.1.66-91.160.amzn2023.x86_64 is an installed security update 
Security: kernel-6.1.55-75.123.amzn2023.x86_64 is the currently running version

```
Can you run `uname -r` to verify that the listed kernel version, i.e. 6.1.66-91.160, or higher is running?
```
[ec2-user@al2023 ~]$ uname -r
6.1.79-99.164.amzn2023.aarch64
```
Motd may need to be updated. Try running this command and verify again
```
cat /etc/motd
sudo update-motd
cat /etc/motd
```

Edit: From kernel version(6.1.38-59.109), your AL2023 is at [version 2023.1.20230809](https://docs.aws.amazon.com/linux/al2023/release-notes/relnotes-2023.1.20230809.html).  You can verify with `dnf info system-release` command

To check for newer release
```
dnf check-release-update
```

To upgrade to latest version which is [2023.3.20240312](https://docs.aws.amazon.com/linux/al2023/release-notes/relnotes-2023.3.20240312.html) as of time of writing
```
sudo dnf update --releasever=2023.3.20240312
```
Reboot after patching
If this still does not work, you could have hard-coded the kernel version. I would check the /etc/default/grub  and /boot/grub2/grubenv files
For example, this is my /etc/default/grub and grubenv file
```
GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200n8 nvme_core.io_timeout=4294967295 rd.emergency=poweroff rd.shell=0 selinux=1 security=selinux quiet"
GRUB_TIMEOUT=0
GRUB_DISABLE_RECOVERY="true"
GRUB_TERMINAL="ec2-console"
GRUB_ENABLE_BLSCFG="true"
GRUB_X86_USE_32BIT="true"
GRUB_DEFAULT=saved
GRUB_UPDATE_DEFAULT_KERNEL=true
```
```
# GRUB Environment Block
# WARNING: Do not edit this file by tools other than grub-editenv!!!
boot_success=1
boot_indeterminate=0
saved_entry=ec294933b0e603800c8968a77843487b-6.1.79-99.164.amzn2023.aarch64
##################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################################
```

AL2023 how to switch kernel

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