Add or Detect New Hard Disk Online Without Rebooting

As a system admin, We may come into a situation to Add a New Disk or Detect New Hard Disk Online to provide more space for the application installed.

How to detect new hard disk online without rebooting?

This post will help you with How to rescan or detect new hard disk online without rebooting the server.

It is possible to add or remove a SCSI device explicitly, or to re-scan an entire SCSI bus without rebooting a running Linux VM guest.

How to Rescan newly added Disk on Linux?

1. Ensure the required size is added newly online without shutting down or powered off in Hypervisors  such as vmware esx, vmware workstation and Microsoft Hyper-V before carrying out the Virtual Disk increasing activity.

2. Login into the server with user root or any other user with root privilege.

3. Run the below command to list the detected disk as below screenshot shows..

[[email protected] ~]# fdisk -l

Add or Detect a New Hard Disk Online Without Rebooting
detect new hard disk online without rebooting

The above screenshot shows as our linux machine has only single disk of 10GB (/dev/sda).

4. Run the below command to list the entire SCSI device buses,

[[email protected] ~]# ll /sys/class/scsi_host/host?/scan
–w——-. 1 root root 4096 May 11 16:03 /sys/class/scsi_host/host0/scan
–w——-. 1 root root 4096 May 11 15:58 /sys/class/scsi_host/host1/scan
–w——-. 1 root root 4096 May 11 15:58 /sys/class/scsi_host/host2/scan

Above command listed the output of number of SCSI device buses, we have to run each below command for each SCSI device buses.

echo “- – -” > /sys/class/scsi_host/host0/scan

Sample Commands for each SCSI Device Buses,


[[email protected] ~]# echo “- – -” > /sys/class/scsi_host/host0/scan
[[email protected] ~]# echo “- – -” > /sys/class/scsi_host/host1/scan
[[email protected] ~]# echo “- – -” > /sys/class/scsi_host/host2/scan

Thats it, now you can see a newly added disk on linux from fdisk command.

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