What are these partitons and can I delete them

I currently dual boot Windows 10 an Ubuntu, and I am getting ready to delete Windows.

The Ubuntu partitions that I know what they are are sda8,sda6, and sda7.

I assume sda4 is the main Windows partition.

What are sda1, sda2, sda3, and sda9, and can I delete them?

Partitions with a key symbol next to them, are currently in use. These are the ones you should not delete.

You see a column "mount points" in your output. Each partition that has an entry in that column is currently connected to your running Ubuntu system. These are data partitions. The one connected to / is your system partition. So for sure, these are the ones you should not remove in order to keep your system functional.

One more partition is possibly being used by your system even if it is not mounted. That is the swap partition. Such partition can be used as overflow ram, and is never as such mounted. To check whether it is used in your system, run the swapon command. If /dev/sda7 is used, you will see it mentioned in the output. If it is not in the output, it is not used and can be removed. Latest versions of Ubuntu do not use a swap partition anymore. They instead install a swap file, which you see in the output as /swapfile.

The other partitions can be removed without breaking your system. Of course, you do not want to loose user files. Thus, you need to make sure that any personal files that might be on these partitions are backed up to an external drive before you delete the partition.

• sda1 is a recovery partition used for recovery if the installed Windows system has problems.
• sda2 is the EFI partition, essential for booting your system
• sda3 is a Microsoft Reserved Partition, used to store certain software components that previously used hidden sectors.
• sda9 is a very small ntfs formatted partition, apparently with no specific purpose or use.

sda3, sda4, and sda9 could be deleted. The freed contiguous space could be used for a new data partition.

The partitions are quite clearly described on your screenshot.

sda1 is labelled "Recovery". Recovery partition allows to reinstall Windows and restore the computer to its factory default state. If you won't need Windows in the future, you can delete it.

sda2 is the EFI partition which is needed to boot the operating systems in modern computers that use UEFI and not the legacy BIOS to boot the operating system. Don't delete it or your computer will not boot.

sda3 is the Microsoft reserved partition which is used for additional system data that may be used by Windows. If you won't need Windows in the future, you can delete it.

sda4 is probably (as you suggest) the main Windows partition. To be sure, you can just mount in in Disks application and see what's on it.

I'm not sure what is the sda9 partition - from the screenshot it looks that it is located at the very end of the disk. But because it is NTFS formatted, and flagged as msftdata (like sda4) it is probably also something used by Windows, maybe another recovery partition? Probably you can delete it.

sda8 is a bit mysterious. Looks like something you created during Ubuntu installation (as it is ext4 formatted), but why isn't it mounted? Anyway, you said you know what this partition is, so no issue here.

sda6 is a root filesystem of your Ubuntu installation. Of course you should not delete it.

sda7 is a swap partition that your Ubuntu is currently using (it has a key icon next to its name, which indicates it is in use). Don't delete it as well. You can, however, assign swap space to a different partition or to a file on main Ubuntu partition, then it won't be needed anymore.