Patch Rollback and Commitment

Patch Rollback

You may occasionally want to remove a patch and restore the system to its prepatched state. This process is known as patch rollback. For example, if you installed a patch that resulted in unacceptable system behavior, you might choose to roll back this patch. However, rollback is possible only if certain files were saved as part of the patch installation process. During patch installation, the default behavior is to save copies of all files that are replaced by the new patch before the new versions of these files are loaded. These saved files are called rollback files and are the key to making patch rollback possible. When you roll back a patch, these rollback files are restored to the system. You should override the default behavior only if you have a complete understanding of the patch rollback process.

You cannot roll back a patch unless one of the following is true:

You can use the swremove command to roll back a patch (if no dependencies exist for the patch). Use the following command to roll back the patch patch_id:

swremove patch_id

As is true for many SD-UX commands, you can add the -p option to execute the command in preview-only mode. This mode allows you to view output from the command without actual changes occurring. You should initially execute the command in preview mode:

swremove –p patch_id

Advanced Topic: Patch Installation and Rollback Files

When installing patches, you can explicitly specify that rollback files not be saved. To do this, you add the –x patch_save_files=false option to the swinstall command:

$ swinstall –s /tmp/temporary_depot/depot –x autoreboot=true \ -x patch_match_target=true –x patch_save_files=false

Only use the false option if you will never remove a patch under any circumstances.

Patch Commitment

Allowing for patch rollback does come at a cost, because the files required for patch rollback consume disk space. If disk space is an issue on a system, you can commit the patches; a process that deletes the associated rollback files, thereby freeing disk space. If disk space is not an issue on a system, you should avoid committing the patches, and leave rollback files in place. If any patch in a supersession chain is committed, all prior patches in the chain lose the ability to be restored, and the save area disk space for those patches will also be reclaimed.

Do not undertake patch commitment without serious consideration of the consequences. When you commit a patch, simple rollback of the patch is no longer possible. Because of this, you should carefully select which patches should be committed. Good candidates include patches that were thoroughly tested in the environment prior to installation, and patches that have been installed on the system for a significant period of time and have not resulted in unwarranted conditions. Other good candidates are patches that have been superseded multiple times. You should also consider a patch's warning status and its HP rating before committing the patch.

To commit an individual patch, execute the swmodify command on the patch with the patch_commit=true option. To commit the patch patch_id, enter this command:

swmodify -x patch_commit=true patch_id

You can add the -p option to this command so it will be executed in preview-only mode.

Advanced Topic: Patch Cleanup Utility

The patch utility called cleanup allows you to commit all patches that have been superseded a specified number of times. You can execute this command in preview mode in order to see what effect the command will have without actually making any changes. You should always use the preview mode first. This is accomplished by including the -p option. The command has the following format:

cleanup [-p] -c number

The cleanup utility is delivered by the following patches (and their superseding patches):

For example, the following command will execute in preview mode. When executed without the -p option, the command causes all patches superseded three or more times to be committed. The patches to be committed are shown in the output of the command.

$ cleanup -p -c3
### Cleanup program started at 04/13/04 07:17:40
Preview mode enabled. No modifications will be made.
Commit patches superseded at least 3 time(s) on 'some_system'.
Obtaining superseded patch information...done.

The following patches superseded at least 3 time(s) can be committed:

Superseded  # Times Superseded  Disk Space in /var/adm/sw/save  Superseded By
==========  ==================  ==============================  =============
PHKL_23313         3                    66560 bytes             PHKL_26519
PHKL_26233         3                   180224 bytes             PHKL_28267
PHNE_23288         3                    59392 bytes             PHNE_23645
PHNE_26388         4                  6581248 bytes             PHNE_28103
PHNE_28103         3                  6694912 bytes             PHNE_28983
PHSS_21817         5                 12379136 bytes             PHSS_26619
PHSS_26492         3                  8761344 bytes             PHSS_27872
PHSS_26619         4                 14969856 bytes             PHSS_26622
PHSS_26622         3                 27064320 bytes             PHSS_26638

All information has been logged to /var/adm/cleanup.log.
### Cleanup program completed at 04/13/04  07:17:40