Applies to openSUSE Leap 42.2

6 Installing Multiple Kernel Versions


openSUSE Leap supports the parallel installation of multiple kernel versions. When installing a second kernel, a boot entry and an initrd are automatically created, so no further manual configuration is needed. When rebooting the machine, the newly added kernel is available as an additional boot option.

Using this functionality, you can safely test kernel updates while being able to always fall back to the proven former kernel. To do so, do not use the update tools (such as the YaST Online Update or the updater applet), but instead follow the process described in this chapter.

Warning: Support Entitlement

Be aware that you lose your entire support entitlement for the machine when installing a self-compiled or a third-party kernel. Only kernels shipped with openSUSE Leap and kernels delivered via the official update channels for openSUSE Leap are supported.

Tip: Check Your Boot Loader Configuration Kernel

It is recommended to check your boot loader configuration after having installed another kernel to set the default boot entry of your choice. See Section 12.3, “Configuring the Boot Loader with YaST” for more information.

6.1 Enabling and Configuring Multiversion Support

Installing multiple versions of a software package (multiversion support) is enabled by default on SUSE Linux Enterprise 12. To verify this setting, proceed as follows:

  1. Open /etc/zypp/zypp.conf with the editor of your choice as root.

  2. Search for the string multiversion. If multiversion is enabled for all kernel packages capable of this feature, the following line appears uncommented:

    multiversion = provides:multiversion(kernel)
  3. To restrict multiversion support to certain kernel flavors, add the package names as a comma-separated list to the multiversion option in /etc/zypp/zypp.conf—for example

    multiversion = kernel-default,kernel-default-base,kernel-source
  4. Save your changes.

Warning: Kernel Module Packages (KMP)

Make sure that required vendor provided kernel modules (Kernel Module Packages) are also installed for the new updated kernel. The kernel update process will not warn about eventually missing kernel modules because package requirements are still fulfilled by the old kernel that is kept on the system.

6.1.1 Automatically Deleting Unused Kernels

When frequently testing new kernels with multiversion support enabled, the boot menu quickly becomes confusing. Since a /boot partition usually has limited space you also might run into trouble with /boot overflowing. While you may delete unused kernel versions manually with YaST or Zypper (as described below), you can also configure libzypp to automatically delete kernels no longer used. By default no kernels are deleted.

  1. Open /etc/zypp/zypp.conf with the editor of your choice as root.

  2. Search for the string multiversion.kernels and activate this option by uncommenting the line. This option takes a comma-separated list of the following values:

    3.12.24-7.1 keep the kernel with the specified version number

    latest keep the kernel with the highest version number

    latest-N keep the kernel with the Nth highest version number

    running keep the running kernel

    oldest keep the kernel with the lowest version number (the one that was originally shipped with openSUSE Leap)

    oldest+N keep the kernel with the Nth lowest version number

    Here are some examples

    multiversion.kernels = latest,running

    Keep the latest kernel and the one currently running. This is similar to not enabling the multiversion feature, except that the old kernel is removed after the next reboot and not immediately after the installation.

    multiversion.kernels = latest,latest-1,running

    Keep the last two kernels and the one currently running.

    multiversion.kernels = latest,running,3.12.25.rc7-test

    Keep the latest kernel, the one currently running, and 3.12.25.rc7-test.

    Tip: Keep the running Kernel

    Unless using special setups, you probably always want to keep the running Kernel. If not keeping the running Kernel, it will be deleted in case of a Kernel update. This in turn makes it necessary to immediately reboot the system after the update, since modules for the Kernel that is currently running can no longer be loaded since they have been deleted.

6.2 Installing/Removing Multiple Kernel Versions with YaST

  1. Start YaST and open the software manager via Software › Software Management.

  2. List all packages capable of providing multiple versions by choosing View › Package Groups › Multiversion Packages.

    The YaST Software Manager: Multiversion View
    Figure 6.1: The YaST Software Manager: Multiversion View
  3. Select a package and open its Version tab in the bottom pane on the left.

  4. To install a package, click its check box. A green check mark indicates it is selected for installation.

    To remove an already installed package (marked with a white check mark), click its check box until a red X indicates it is selected for removal.

  5. Click Accept to start the installation.

6.3 Installing/Removing Multiple Kernel Versions with Zypper

  1. Use the command zypper se -s 'kernel*' to display a list of all kernel packages available:

    S | Name           | Type       | Version         | Arch   | Repository        
    v | kernel-default | package    | | x86_64 | Alternative Kernel
    i | kernel-default | package    |  | x86_64 | (System Packages) 
      | kernel-default | srcpackage | | noarch | Alternative Kernel
    i | kernel-default | package    |  | x86_64 | (System Packages)
  2. Specify the exact version when installing:

    zypper in kernel-default-
  3. When uninstalling a kernel, use the commands zypper se -si 'kernel*' to list all kernels installed and zypper rm PACKAGENAME-VERSION to remove the package.

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