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VIOS Updates: Harnessing the Power of Alternate Disk Update

By Vikas Sharma posted Fri January 09, 2026 07:47 AM

  

Updateios command updates the Virtual I/O Server to the latest maintenance level. With the release of VIOS 4.1.2.00, a significant enhancement has been introduced: support for updateios on an alternate disk. This feature is designed to improve system availability and reduce risk during updates.

Why It Matters

  • High Availability: Your VIOS stays online during the update.
  • Risk Reduction: Updates happen in isolation, minimizing downtime.
  • Easy Recovery: Simply clean the alternate disk, original root disk stays intact.

How It Works

You can run the updateios command with a new option:

updateios -dev <Media> -install -accept -altdisk <targetDisks>

     altdisk                   Specifies to apply the update on alternate disk(s).

     targetDisks           One or more colon separated list of disks which must be unused & free.

Example:

updateios -dev /home/padmin/UPDATE -install -accept -altdisk hdisk1

After the Update

Once the update completes successfully, you can change the bootlist to boot VIOS from the alternate disk by running the following command

bootlist -m normal -o <alternate_disk#>

Recovery Steps in Case of Failure

If the update on the alternate disk fails:

  1. Do not change the bootlist — keep the system booting from the original disk.
  2. Check the console logs of updateios for any errors.
  3. Run $ alt_root_vg -remove to delete the altinst_rootvg Volume Group.
  4. Re-run updateios after fixing the issues. Choose a different alternate disk or clean and reuse the used one. You will have to run $ cleandisk -f -c alternate_disk command to clean disk to mark it as free. 

Traditional vs Alternate Disk Update

Feature

Traditional Update

Alternate Disk Update

Risk of downtime

High

Low

Recovery complexity

High

Minimal

Contacting the PowerVM Team

Have questions for the PowerVM team or want to learn more?  Follow our discussion group on LinkedIn IBM PowerVM or IBM Community Discussions

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