To update all packages on a Red Hat Enterprise Linux (RHEL) or CentOS system using the "yum" package manager, except for the Linux kernel, you can use the following command:
yum update --exclude=kernel*
This will update all of the packages on the system, except for packages that have "kernel" in their name. The "--exclude" option tells "yum" to exclude the specified packages from the update.
Alternatively, you can use the "yum update-minimal" command, which will only update the packages that are necessary to fix security vulnerabilities or bugs. This will typically include all of the packages on the system, except for the Linux kernel.
For example:
yum update-minimal
This will update all of the packages on the system that need to be updated, without updating the Linux kernel.
Keep in mind that updating the Linux kernel may be necessary to fix security vulnerabilities or other issues, and you should carefully consider the impact of not updating the kernel before doing so. If you are unsure about how to proceed, you may want to seek guidance from a system administrator or the RHEL or CentOS community.