The Live Update concepts

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In the AIX® Live Update function, the logical partition (LPAR) where the operation is started is called the original partition. The operation involves another LPAR that is called the surrogate partition. Checkpointing a workload means freezing a running process and saving its current state. Checkpointing processes on an LPAR and restarting them later on another LPAR is called mobility.

If you plan to install updates by using the Live Update function, before you begin the installation, you must back up your system so that you can return to the previous operating level, if necessary, by restoring the system from the backup or by restarting your system from an alternate disk copy. The updates that are installed by using the Live Update function are always committed. Therefore, you cannot reject the updates later.

The updates for a service pack, technology level, and interim fixes are applied before starting the surrogate partition, and the running workloads are transferred from the original partition to the surrogate partition. The Live Update process involves the following steps:

  1. If updates to a service pack or technology level are specified to be installed by using the Live Update function, the updates are applied and committed first on the original partition.
  2. If any interim fixes are specified along with the service pack and technology level updates, the interim fixes are installed on the original partition.
  3. The root volume group of the original partition (orig-rootvg) is cloned.
  4. If only interim fixes are specified for the Live Update operation, the interim fixes are applied on the cloned volume group that serves as the boot volume group for the surrogate partition (surr-boot-rootvg).
  5. After the surrogate partition is started and while the workloads are still running on the original partition, the root volume group of the surrogate partition is mirrored (surr-mir-rootvg).
  6. The workload processes are check pointed and moved to the surrogate partition.
  7. Workloads resume on the surrogate partition in a chrooted environment (changed root directory) on the original root volume group (orig-rootvg). During this process, the workloads continue to run without being stopped, although a short blackout time occurs when these workloads are suspended.
  8. If the Live Update operation fails after step 1 and step 2, the updates and interim fixes installed on the system in these steps are not uninstalled. If the cause of the Live Update failure is corrected, you can attempt the Live Update operation again instead of restarting the original LPAR. In this scenario, updates or interim fixes are not specified for the Live Update operation because the updates are already installed.

The Live Update feature is intended for applying interim fixes that contain kernel changes or kernel extension changes that require a reboot. The interim fix might contain other files (for example, commands and libraries), and the Live Update feature does not change anything about the way these files are applied. For example, a shared library will be modified on the file system, but any running processes continues to use the old version of the library. Therefore, applications that require a library fix must be stopped and restarted to load the new version of the library after the fix is applied. In AIX® Version 7.2 with the 7200-01 Technology Level, or later, you can use the genld -u command to list the processes that are using the old version of any shared libraries or other objects that are updated. You can use the list that is displayed from the genld -u command to identify the processes that must be stopped and restarted to load the updated objects.

The Live Update operation is not a stand-alone command. It can be launched only through the geninstall -k option or Network Installation Manager (NIM). The inputs to the Live Update operation are supplied through the stanzas in the /var/adm/ras/liveupdate/lvupdate.data file. A template of this file is supplied with the system. You must edit this file to reflect your own configuration. The geninstall command uses a lock file, /usr/lpp/.genlib.lock.check, to guarantee that no other installation process can run simultaneously. A special line INU_LKU_LOCK in this lock file is used to indicate that other installations must be blocked. In another scenario, NIM can be used with the -o cust option from a centralized server to invoke the geninstall command on a target machine. In this case, the /var/adm/ras/liveupdate/lvupdate.data file is exported by the NIM master and mounted by the NIM client on the target machine.

The Live Update operation runs in one of the following modes:

Preview mode
In preview mode, estimation of the total operation time, estimation of application blackout time, and estimation of resources such as storage and memory are provided to the user. These estimations are based on the assumption that the surrogate partition has the same resources in terms of CPU, memory, and storage as the original partition. All the provided inputs are validated and the Live Update limitations are checked.
Automated mode
In automated mode, a surrogate partition with the same capacity as the original partition is created, and the original partition is turned off and discarded after the Live Update operation completes.

The mirror copy of the original root volume group (rootvg) is retained after the Live Update operation is complete. Thus, if you have installed only interim fixes with the Live Update function and if you want to return to the state of the system before you applied the interim fixes, the LPAR can be restarted from the disk that was specified as the mirror volume group (mirrorvg).

Alternatively, you can choose to install any updates or interim fixes on the original LPAR by using any installation method that is supported by the AIX® operating system. After these updates or fixes are installed, you can use the Live Update function to load the updated kernel software without restarting the system. The Live Update process for this scenario involves the following steps:

  1. Back up the system by using your preferred backup method. A backup is required if you want to restore the system to its previous state before the updates or interim fixes were installed.
  2. Install the updates and interim fixes by using any supported installation method (Network Installation Manager (NIM) or installp).
  3. If you must restart the system to apply the updates or interim fixes, you can use the Live Update function instead of restarting the system. The Live Update operation starts either through the geninstall command or NIM. The Live Update operation does not require you to specify any updates or interim fixes because the updates are installed on the system.
  4. The root volume group of the original partition (orig-rootvg) is cloned.
  5. After the surrogate partition is started and while the workloads are still running on the original partition, the root volume group of the surrogate partition is mirrored (surr-mir-rootvg).
  6. The workload processes are check pointed and moved to the surrogate partition.
  7. Workloads resume on the surrogate partition in a chrooted environment (changed root directory) on the original root volume group (orig-rootvg). During this process, the workloads continue to run without being stopped, although a short blackout time occurs when the workloads are suspended.
  8. If the Live Update operation fails, correct the cause of the failure, and retry the process starting at step 3.