6 Replies Latest reply on Jul 15, 2020 8:30 PM by vkenneth

    Expand Space without Rebooting VM

    curiousmind999 Lurker

      Hi, is there a way that I can expand virtual disk space without rebooting VM.


      I know that there is a command to recognize the device, but the device is already recognized (such as /dev/sdc), But now I need the OS (Linux) to recognize the additional space without rebooting.


      Re-scan the SCSI Bus to Add a SCSI Device Without rebooting the VM using the following command

      echo "- - -" > /sys/class/scsi_host/host#/scan  
        • 1. Re: Expand Space without Rebooting VM
          XavierEstevez Novice

          Fair warning:

          -You should definitely back up this VM before proceeding.

          -It's best to practice this on a testing VM with the same OS to verify it'll work.

          -You might end up having to reboot anyway.


          Check out http://blog.pluralsight.com/resize-vmware-linux-drives assuming you're using RHEL.


          One thing I've found is that sometimes fdisk does not correctly report the increased size of the disk, but cfdisk will. So if you did this to SDC, try:

          sudo cfdisk /dev/sdc

          and see if your extra space shows up there.


          Good luck!

          1 person found this helpful
          • 2. Re: Expand Space without Rebooting VM
            curiousmind999 Lurker



            The article helped!


            • 3. Re: Expand Space without Rebooting VM
              vuzzini Hot Shot

              Hello Curiousmind999,

              Once you've changed the disk's size in VMware and did not reboot your server, rescan your SCSI devices as such.

              First, check the name(s) of your scsi devices.

              $ ls /sys/class/scsi_device/

              Then rescan the scsi bus. Below you can replace the '0\:0\:0\:0′ with the actual scsi bus name found with the previous command. Each colon is prefixed with a slash, which is what makes it look weird.

              ~$ echo 1 > /sys/class/scsi_device/0\:0\:0\:0/device/rescan

              That will rescan the current scsi bus and the disk size that has changed will show up.

              • 4. Re: Expand Space without Rebooting VM
                KpuCko Lurker


                root@debiantestlvm:~# echo "- - -" > /sys/class/scsi_host/host0/scan

                root@debiantestlvm:~# echo "- - -" > /sys/class/scsi_host/host1/scan

                root@debiantestlvm:~# echo "- - -" > /sys/class/scsi_host/host2/scan

                • 5. Re: Expand Space without Rebooting VM
                  blentzz Lurker

                  Sorry for posting on a thread that's so old, but this is the destination for many a google search, I suspect. And you've asked a valid question that deserves an explanation.


                  There's a difference between rescanning for new disks at the adapter level and rescanning for update size information at the disk level.


                  Sending "- - -" to /sys/class/scsi_host/host[012]/scan is telling the SCSI host adapter to look for new disks on every channel "(-)", every target "(-)", and every lun "(-)". - this is the right thing to do if you add a new disk to the system while it's powered on.


                  Sending a "1" to /sys/class/block/sdc/device/rescan is telling the SCSI block device to refresh it's information about where it's ending boundary is (among other things) to give the kernel information about it's updated size. - this is the right thing to do if you change the size of an existing disk while it's powered on.



                  • 6. Re: Expand Space without Rebooting VM
                    vkenneth Lurker

                    This an old thread but is the first hit when you search for this task.

                    blentzz  has provided the correct answered and helped me resolve this issue.