What is a boot device?
A boot device refers to the storage device that contains the operating system and files needed to boot up or start a computer. When you turn on your computer, it loads the operating system from the designated boot device in order to initialize the hardware, load drivers, and launch the user interface.
The most common boot devices are internal hard drives or solid state drives. External drives like USB flash drives can also be configured as boot devices. Older computers may have used optical media like CDs or DVDs as boot devices. Network boot over LAN is another option.
No matter the physical storage medium, the boot device contains the bootloader and other critical software needed for the boot process. The computer’s BIOS or UEFI firmware is hardwired to try booting from specific devices in a priority order defined by the boot order configuration. Identifying the current boot device can help troubleshoot issues like boot failures.
Overall, the boot device contains the system files required to fully load the operating system at startup. It is the first storage device accessed once a computer is powered on.
https://www.seslisozluk.net/en/what-is-the-meaning-of-boot-device/
Why do you need to know the boot device?
There are several common situations where you may need to identify or change the boot device on your computer:
Reinstalling the operating system – When reinstalling Windows, Linux, or another operating system, you often need to boot from the installation media. Knowing how to change the boot order to boot from CD/DVD or USB is important.1
Dual booting – If you want to install a second operating system for dual booting, you’ll need to make sure the boot order is set up properly to choose which OS to start. You need to know the boot device for each OS.2
Troubleshooting boot issues – Errors like “No boot device found” often mean your BIOS/UEFI can’t find a valid boot device. Knowing how to check and change the boot device is important for troubleshooting.3
Hardware changes – Adding or changing hard drives may change your boot device. You may need to update the boot order to start from the new drive.
Startup preferences – Some people want to always boot from a certain device for performance reasons. Knowing the boot device allows you to set the preferred startup disk.
BIOS/UEFI boot order
The BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) controls the boot process and boot sequence on most computers. It contains configuration settings for your hardware, including the boot order which determines which device the computer tries first when booting up.
The boot order list may include the hard drive, optical drives, USB drives, network interface card, etc. The computer will attempt to boot from the device at the top of the boot order list first. If no bootable media is found there, it moves down to the next item on the list until a system disk with a bootable operating system is located.
You can access the BIOS/UEFI setup utility on most computers by pressing a special key during the boot process. Common keys are F2, F10 or Delete. Once in the BIOS, look for options related to boot order or priority. The boot devices will be listed in the order they are checked. To change the boot order, highlight a device and use the on-screen options to move it higher or lower in the list.
Setting the correct boot order ensures your preferred boot device, usually the hard drive, is first in the sequence so your operating system loads normally. Getting the order wrong could result in booting to the wrong device or getting an error because no bootable media is detected.
Check boot order in Windows
You can check the boot order in Windows using the msconfig utility. Here are the steps:
- Open the Run dialog by pressing Windows Key + R.
- Type “msconfig” and click OK to open the System Configuration utility.
- Go to the Boot tab.
- You will see the current boot order listed under “Boot Options.” This lists the devices and their order that Windows will check when booting up.
The device at the top will be the first boot device, followed by the next device, and so on. Typically you will see the hard drive or SSD that Windows is installed on at the top. Other devices like removable drives may be listed lower down.
If you need to change the boot order, you can use the up and down arrows to reorder the list of devices. Make sure to click “OK” and restart your computer for any changes to take effect.
Checking the boot order here in msconfig is useful for diagnosing boot issues if your computer is not booting from the correct drive.[1]
Check boot order in Linux
To check the boot order in Linux, you can view the GRUB configuration file located at /etc/default/grub. This file defines the default boot entry for GRUB as well as the boot menu order. Here are the steps to view the boot order:
- Open a terminal window.
- Edit the GRUB configuration file with a text editor like nano:
sudo nano /etc/default/grub - Look for the GRUB_DEFAULT line. This defines the default boot menu entry, numbered from 0.
- The GRUB_TIMEOUT line defines how many seconds the boot menu is displayed.
- The order of entries in the GRUB boot menu is defined in /boot/grub/grub.cfg, which is generated from /etc/grub.d. Do not edit this file directly.
To permanently change the boot order, edit the /etc/default/grub configuration file. Change the GRUB_DEFAULT number to the entry you want to boot by default. Save the changes and run sudo update-grub to regenerate grub.cfg.
You can also temporarily change the boot order for the next reboot from the GRUB menu. Press and hold Shift during boot to access the GRUB menu. Use the arrow keys to select the desired entry and press Enter to boot.
For more details on Linux boot options, refer to the Red Hat documentation.
Check boot partitions
To identify which partition is your boot partition, you can use a partition tool like GParted (Linux) or Disk Management (Windows) to view all disks and partitions. The boot partition is usually labeled as:
- Linux – /boot partition, ext2 or ext4 filesystem
- Windows – System Reserved partition, NTFS filesystem
On Linux, the boot partition is often around 500MB-1GB in size. On Windows, the System Reserved partition is usually 100-350MB. You can confirm it is the boot partition by right-clicking on it in your partition tool and looking at the details.
Additionally, you can run commands like df -h (Linux) or mountvol (Windows) to view partitions and identify the one mounted as /boot or System Reserved. This will definitively tell you the boot partition based on the mount point.
If you still cannot identify the boot partition, you may need to refer to the original disk setup or reinstall documentation to determine which partition was designated for boot files. Knowing the typical size and filesystem can help narrow it down.
Identify from boot loader
One way to find your boot device is to look in your boot loader menu. On most Linux systems, this will be the GRUB (GRand Unified Bootloader) menu.
When your computer first starts, you can access the GRUB menu by pressing the Shift key during bootup. This will display a list of available operating systems and kernel versions to boot into.
The GRUB menu will show all available boot devices and partitions. Typically the boot device will be listed first, with the name of the drive and partition, such as “/dev/sda1”. This indicates that the GRUB bootloader files are located on the first partition of the first drive.
You can also drop to the GRUB command line by pressing C or F2/F10 (varies by distribution). Then you can use the ls command to list devices, partitions, and filesystems seen by GRUB. For example:
grub> ls (hd0) (hd0,gpt2) (hd0,gpt1)
This shows that GRUB has detected hard drive 0, with partitions gpt1 and gpt2. The device in parentheses is likely the boot device.
On a system booted in BIOS/MBR mode, the devices may be listed as (hd0,msdos1) instead of gpt. But the principle remains the same – the first device listed is typically the boot device.
Seeing the boot device right in the GRUB menu is the most straightforward way to identify it from the bootloader directly. Just be sure to note the drive name and partition.
Sources:
https://superuser.com/questions/1258525/how-do-i-list-my-devices-in-grub
https://askubuntu.com/questions/1179371/how-can-i-find-the-drive-name-grub-is-using-for-booting
Check mount points
The boot partition is the partition that contains the bootloader files necessary for booting your operating system. This partition is mounted at a specific mount point, which allows the operating system and applications to access the files on that partition.
On Linux systems, the boot partition is commonly mounted at ‘/boot’. You can check which partition is mounted there by running:
mount | grep '/boot'
This will show the partition mapped to ‘/boot’, which is typically your boot partition. For example, it may show:
/dev/sda1 on /boot type ext4 (rw)
Indicating that ‘/boot’ is mounted from the ‘/dev/sda1’ partition. The ‘rw’ indicates it is mounted read-write.
Some Linux systems may use separate partitions for ‘/boot’ and ‘/boot/efi’ for UEFI systems. So you may need to check both locations. The key is finding which partition contains the bootloader files like grub or systemd-boot.
On Windows, the typical boot partition is ‘C:’, but you can double check by looking at the ‘Boot’ volume in Disk Management. This will confirm if ‘C:’ or another drive letter holds your bootloader files.
Checking the mount point is a quick way to identify the current boot partition from both Linux and Windows.
Use Disk Utility
One easy way to identify your boot device on Mac is by using Disk Utility. Disk Utility allows you to see information about all the disks and volumes connected to your Mac.
To open Disk Utility on Mac, go to Applications > Utilities > Disk Utility. In the sidebar, you will see a list of all available disks and volumes. Click on each disk to inspect it.
In the main view, you can see details like the partition map scheme, number of partitions, mount points, format type, and more. This can help you identify which disk contains your boot volume.
For example, your boot disk will likely show a partition with the format “APFS” and mount point “/”. The disk name will be something like “Mac SSD” or “Macintosh HD”.
You can also click “Show All Devices” in the top left view menu to see disks that are normally hidden, including recovery partitions and bootcamp partitions. This provides additional insight into potential boot devices (Apple Support).
Overall, Disk Utility provides an easy graphical way to inspect disks and identify your system’s boot device on Mac.
Boot from external media
Sometimes the easiest way to identify your system’s boot drive is to boot from external media like a USB drive. By booting from an external USB drive, you can then view your system’s internal drives and identify which one is set as the primary boot device.
Follow these steps to boot from a USB drive on a Windows PC:
- Insert a bootable USB drive into your computer.
- Reboot your computer and enter the BIOS/UEFI settings menu, usually by pressing F2, F10 or Delete during startup.
- In the BIOS settings, go to the Boot tab and select your USB drive as the first boot device.
- Save changes and exit BIOS to reboot from the USB drive.
- Once booted into the USB environment, open the disk utility and identify which internal drive is marked as the boot drive.
- Reboot back into BIOS and reset your internal hard drive as the first boot device before exiting.
Booting from a Linux live USB is similar – just choose the USB drive first to boot from, then you can view the internal drives and identify the Windows or other OS boot drive that way.
Using external media to boot allows you to clearly see your internal drives and identify which one your system boots from by default. Just be sure to reset your original internal boot drive as first priority after identifying it.