How to unencapsulate the rootdisk

Problem

The following is the procedure for manual un-encapsulation:

Solution

This procedure is only applicable to Volume Manager versions 4.0 and higher. Versions 4.0 and higher do not require rootdg.

You can use vxunroot. to unencapsulate the bootdisk. Refer to article 244678  linked with this article.

Vxunroot will complain if the underlying partition for the volumes in rootdg does not exist. In that case,  you would need to unencapsulate the bootdisk manually.

Note: With the older versions of VxVM, Volume Manager would convert partitions from the rootdisk to volumes and would wipe off the under lying partitions for anything other then root, var, swap and user.

Before unencapsulating the bootdisk manually, confirm with the prtvtoc command the existence of the underlying partitions for any of the root file systems like /opt /export...

You can refer to  article 199001 linked to this article for the instructions on how  to add the missing underlying partition/s

The following is the procedure for manual un-encapsulation:

1.  Prevent Volume Manager from starting on boot:
# touch /etc/vx/reconfig.d/state.d/install-db

2. Save a copy of /etc/vfstab, and /etc/system file.

3. Copy the original vfstab (vfstab.prevm)  to vfstab.
# cp /etc/vfstab.prevm /etc/vfstab

4.  vi /etc/system an  remove the two following lines:
rootdev:/pseudo/vxio@0:0
set vxio:vol_rootdev_is_volume=1

5. # Reboot the server and make sure the system comes up without Volume Manager.

Once the system is back up:

Start Volume Manager manually:
a. rm /etc/vx/reconfig.d/state.d/install-db
b. vxconfigd -m disable
c. vxiod set 10
d. vxdctl enable

The root disk is now unencapsulated. You can quickly verify this with the df -k command. The root file systems will be mounted on slices instead of volumes.

At this point, rootdg will still exist and a vxprint of rootdg may still show active volumes. However, all I/O will be directed through slices and not through volumes. It is specifically NOT recommended that the procedure be reversed in order to reencapsulate the root disk. Because I/O has been done on the slices outside of Volume Manager, there is a significant risk of data corruption on the root volumes if the procedure is reversed.

Cleanup of rootdg and reencapsulation of the root disk should be evaluated on a case by case basis and is outside the scope of this article.