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Alternate Disk Installation: 

AIX  has the ability to copy the contents of the root VG to another harddisk through alternate disk installation because the alternate disk installation process involves cloning an existing rootvg to a target alternate disk, the target alternate disk must not be already assigned to a volume group.

Alternate disk installation, available starting with AIX Version 4.3, allows for system installation on a system while it is still up and running. Install or upgrade downtime decreases considerably. It also allows large facilities to manage an upgrade, because systems can be installed over a longer period of time, while the systems are still running at the existing version. The switch over to the new version can then happen with a simple reboot, with the possibility to roll back to the original situation in case of problems.

/var/adm/ras/alt_disk_inst.log                       alt_disk log file

Alternate disk installation can be used in one of two ways:

1. Cloning the current running rootvg to an alternate disk.

Note: In this way, you have an online backup available, at the cost of one or more physical disks.

2. Installing a mksysb image on another disk.

Filesets required:

bos.alt_disk_install.boot_images  filesets must be installed for alternate disk mksysb installation, if Network Install Management (NIM) is not being used.

The bos.alt_disk_install.rte  fileset must be installed to clone rootvg.


Once you have installed these filesets, the alternate disk installation functions are available to you in the Software Installation and Maintenance menu. Use the SMIT fast path:

#smitty alt_install


Alternate disk rootvg cloning:

Cloning the rootvg to an alternate disk can have many advantages:

1.  Having an online backup available in case of disaster. Keeping an on-line backup requires that an extra disk or disks to be available on the system.

2.  Applying new maintenance levels or updates. A copy of the rootvg is made to an alternate disk, then updates are applied to that copy. Finally, the boot list is updated to boot from the new device. The system runs uninterrupted during this time. When it is rebooted, the system will boot from the newly updated rootvg for testing. If updates cause problems, the old rootvg can be retrieved by resetting the bootlist and rebooting.

To clone your rootvg to a new disk, do the following procedure:

1. Use the SMIT  #smitty alt_install or fast path smitty alt_clone


2. In the Target Disk(s) to install field, enter the name of the disk you want to use for making the clone. The target disk should be a stand-alone disk not belonging to a volume group. In addition to this, SSA disks cannot be used as your target disks.

3. The Phases to execute field defaults to all. Accept the default, for now.

4. In the Exclude list field, you can create a file that will contain the names of all the files and directories that you do not want to be copied to your cloned system.

5. Specify the name of any additional bundles or filesets and fixes that you want to install in the Bundle to install and Fix to Install fields. The use of these fields allows service to be installed as part of the clone process.

6. Specify the name of the input device in case you have selected to install any additional software in the Directory or Device with images field.

7. If you want your system to start from your alternate rootvg on the next system start-up, set the Set the bootlist to boot from this disk on next boot to YES.

8. Press Enter.

By default, using the alt_disk_install command does the following:

1. Creates an /image.data file based on the current rootvg’s configuration. A customized image.data file can be used.

2. Creates an alternate rootvg (altinst_rootvg).

3. Creates logical volumes and file systems with the alt_inst prefix.

4. Generates a backup file list from the rootvg, and if an exclude.list file is given, those files are excluded from the list.

5. Copies the final list to the altinst_rootvg’s file systems.

6. If specified, the installp command installs updates, fixes, or new filesets into the alternate file system.

7. The bosboot command creates a boot logical volume on the alternate boot disk.

8. If a customization script is specified, it runs at this point.

9. The file systems are then unmounted, and the logical volumes and file systems are renamed.

10.The logical volume definitions are exported from the system to avoid confusion with identical ODM names, but the altinst_rootvg definition is left as an ODM placeholder.

11.By default, the bootlist is set to the new cloned rootvg for the next reboot.

If you are performing a clone installation, device information will not be restored to the target system by default. During a clone installation, the BOS installation process verifies that the mksysb image is from the system you are trying to install. If the target system and the mksysb image are different, the device information is not recovered. This behavior is determined by the RECOVER_DEVICES variable in the bosinst.data file. This variable can be set to Default, yes, or no. The following list shows the resulting behaviors for each value:


No recovery of devices


Attempted rebuild of ODM


No recovery of devices

Note: You can override the default value of RECOVER_DEVICES by selecting yes or no in the Backup Restore menu or by editing the value of the attribute in the bosinst.data file.


alt_disk_copy creates copies of rootvg on an alternate set of disks.

#alt_disk_copy -d <hdiskx>   (clone the rootvg to the specified disk)

#alt_disk_copy -e /etc/exclude.rootvg -d  <hdiskx> ( -e is use the exclude list during the cloning )

#alt_disk_copy  -T -d <hdiskx>  (convert jfs to jfs2 on the new target disk (from 6.1 TL4 only))

#alt_disk_copy   -d <hdiskx> -b update_all -l <TL level path>  (this will do the update )

alt_rootvg_op  performs Wake, Sleep, and Customize operations.

#alt_rootvg_op  -X <cloned rootvg>  destroy the cloned rootvg

#alt_rootvg_op -v <new name of cloned rootvg> -d <hdiskx> rename the given cloned rootvg name

2. Alternate mksysb install: 

An alternate mksysb install involves installing a mksysb image that has already been created from another system onto an alternate disk of the target system. The mksysb image (AIX Version 4.3 or later) would be created on a system that was either the same hardware configuration as the target system or would have all the device and kernel support installed for a different machine type or platform or different devices.

To create the alternate mksysb system, use the SMIT #smitty alt_install or fast path:

1. smitty alt_mksysb


2. Enter the name of the disk on which you want to install the mksysb in the Target Disk(s) to install field.

3. Enter the name of the device or the image name from which you will be restoring the mksysb in the Device or image name field.

4. Press Enter.

Once the mksysb image is restored to the new disk, the system reboots from the new alternate rootvg. This completes your alternate mksysb installation.

Commands :

alt_disk_mksysb installs an existing mksysb on an alternate set of disks.

#alt_disk_mksysb -m <mksysb image path> -d <hdiskx> (install a mksysb to specified disk)

#alt_disk_mksysb  -B  -T  -m <mksysb image path> -d <hdiskx> (convert the file system from a JFS file system to a JFS2 file system )\

-B   Specifies not running bootlist after the operation. If set, then the -r flag cannot be used.

-r   Specifies to reboot from the new disk when the alt_disk_mksysb command is complete.

-T   Indicates that you want to convert JFS file systems to JFS2 file systems during the process of recreating the rootvgvolume group on      target disks.