Topics: AIX, Hardware, Storage, System Admin

Creating a dummy disk device

At some times it may be necessary to create a dummy disk device, for example when you need a disk to be discovered while running cfgmgr with a certain name on multiple hosts.

For example, if you need the disk to be called hdisk2, and only hdisk0 exists on the system, then running cfgmgr will discover the disk as hdisk1, not as hdisk2. In order to make sure cfgmgr indeed discovers the new disk as hdisk2, you can fool the system by temporarily creating a dummy disk device.

Here are the steps involved:

First: remove the newly discovered disk (in the example below known as hdisk1 - we will configure this disk as hdisk2):

# rmdev -dl hdisk1
Next, we create a dummy disk device with the name hdisk1:
# mkdev -l hdisk1 -p dummy -c disk -t hdisk -w 0000
Note that running the command above may result in an error. However, if you run the following command afterwards, you will notice that the dummy disk device indeed has been created:
# lsdev -Cc disk | grep hdisk1
hdisk1 Defined    SSA Logical Disk Drive
Also note that the dummy disk device will not show up if you run the lspv command. That is no concern.

Now run the cfgmgr command to discover the new disk. You'll notice that the new disk will now be discovered as hdisk2, because hdisk0 and hdisk1 are already in use.
# cfgmgr
# lsdev -Cc disk | grep hdisk2
Finally, remove the dummy disk device:
# rmdev -dl hdisk1

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