[SOLVED] How to identify the New LUN assigned to redhat system ? If there is multiple devices or LUN already

dev008 · 09-22-2016, 04:05 PM

I have requested for a new LUN assignation of 100GB on my RedHat system. But there is already many devices which have size with 100GB, so how to identify the new lun on the system with size of 100GB.

Thanks in advance.

jpollard · 09-22-2016, 05:18 PM

It should be the one without a UUID. The blkid utility will list known devices with their UUID - but an uninitialized lun will not have a UUID.

A bit tricky, but compare the first column of the blkid output and the last column of the contents of /proc/partitions.

The /proc/partitions will list all devices and their size - as well as any partitions on those devices. The new one should be the entry in /proc/partitions that doesn't exist in blkid list.

Now, this is assuming the device is known as after a reboot. It is possible to force a rescan of devices (https://blogs.it.ox.ac.uk/oxcloud/20...e-new-storage/), but that may depend on your controllers (works for SAS/SATA, but I don't know how fibre channel devices would go).

dev008 · 09-22-2016, 05:25 PM

Hi jpollard,

Thanks for your replay on the post.

jpollard · 09-22-2016, 05:30 PM

Welcome.

There are sometimes faster ways but they depend on knowing how the system is configured first.

One is knowing if all devices are given partitions. Thus for sdx in /proc/partitions there will be an sdx<n> where n is the partition on device sdx.

The new device will not be partitioned, so there will only be the sdx entry - unless someone already partitioned it...

Even the method I gave first is vulnerable to that - the person creating the lun may have initialized it to verify it was working properly... And that might give it a UUID.

ardvark71 · 09-22-2016, 06:13 PM

Hello and welcome to the forum

Just as a suggestion, you might want to change your username using the instructions at the top of the page here, lest your email inbox ends up with a boatload of SPAM in the very near future. The "Contact Us" form is here.

Regards...

dev008 · 09-23-2016, 03:22 AM

Hi ardvark71,

Thanks for your suggestion.

Really I was trying to change my user name but unable to change, so I have just sent you the mail please change my user name as soon as possible.

ardvark71 · 09-23-2016, 12:19 PM

Quote:

Originally Posted by dev008

Thanks for your suggestion.

You're welcome

Quote:

Originally Posted by dev008

Really I was trying to change my user name but unable to change, so I have just sent you the mail please change my user name as soon as possible.

I'm not the owner or one of the moderators, they would be the ones to take care of that and from the looks of it, they already did.

Regards...