How to Rescan Disks in Ubuntu

How to Rescan Disks in Ubuntu

In web hosting, especially when dealing with dedicated servers and VPS servers, it’s crucial to understand the intricacies of disk management. One of the common tasks that administrators often need to perform is rescanning disks. This is particularly relevant when you’ve added new storage or made changes to your existing storage configuration.

Ubuntu, a popular Linux distribution often used in cloud hosting and shared hosting environments, provides tools and commands that allow users to rescan disks without requiring a system reboot. This is especially useful in production environments where uptime is critical.

Whether you’re running a web server with Apache, Nginx, or LiteSpeed, understanding how to manage and rescan disks is essential. In this tutorial, we will dig into the steps required to rescan disks in Ubuntu, ensuring that your system recognizes any new storage devices or changes made to existing ones.

Step 1: Open the Terminal

Before you can execute any commands, you need to open the terminal. This can be done by pressing “CTRL + ALT + T” or searching for “Terminal” in the application menu.

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Step 2: Identify the Disk

Use the following command to list all the available disks and their partitions:

sudo fdisk -l

Step 3: Rescan a Specific Disk

If you know the name of the disk (e.g., /dev/sda), you can rescan it using the following command:

echo "- - -" | sudo tee /sys/class/scsi_host/hostX/scan

Replace hostX with the appropriate host number. This can usually be found in the /sys/class/scsi_host/ directory.

Step 4: Rescan All Disks

If you want to rescan all disks, you can use a loop:

for host in /sys/class/scsi_host/host*; do echo "- - -" | sudo tee $host/scan; done

Step 1: Verify the Changes

After rescanning, you should verify that the system recognizes the new or changed disks. You can use the fdisk -l command again to check.


  1. Why do I need to rescan disks in Ubuntu?

    Rescanning disks in Ubuntu is essential when you’ve added new storage devices or made changes to existing storage configurations. Instead of rebooting the entire system, which can disrupt services and users, rescanning allows the system to recognize these changes while it’s still running. This ensures that the system is up-to-date with the latest storage configuration without affecting uptime.

  2. Can I rescan disks without sudo privileges?

    No, rescanning disks requires root privileges because it involves accessing and modifying system-level configurations. Using the ‘sudo’ command ensures that you have the necessary permissions to perform the operation. Always exercise caution when using root privileges and ensure you understand the commands you’re executing.

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Commands Mentioned

  • sudo fdisk -l – Lists all available disks and their partitions.
  • echo “- – -” | sudo tee /sys/class/scsi_host/hostX/scan – Rescans a specific disk.
  • for host in /sys/class/scsi_host/host*; do echo “- – -” | sudo tee $host/scan; done – Rescans all disks.


Managing storage is a fundamental aspect of server administration. Whether you’re dealing with a dedicated server, a VPS server, or even a cloud hosting environment, understanding how to efficiently and safely manage your storage resources is crucial. Rescanning disks in Ubuntu, as we’ve explored in this tutorial, is a straightforward process that ensures your system is always aware of its storage configuration.

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The ability to rescan disks without a system reboot is especially beneficial in production environments. It minimizes disruptions and ensures that services remain available to users. Moreover, with the increasing complexity of web servers like Apache, Nginx, and LiteSpeed, having a solid grasp of storage management becomes even more critical.

In conclusion, while the commands and steps to rescan disks in Ubuntu are relatively simple, their importance cannot be understated. Regularly checking and managing your storage ensures that your server runs efficiently and that you can quickly adapt to changes or expansions in your storage needs. As always, exercise caution when executing commands with root privileges and ensure you have backups in place for critical data. With the knowledge from this tutorial, you’re well-equipped to manage and rescan disks in Ubuntu effectively.


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