I am currently on Centos 7 and I am trying to free up some space on one of my disks so I can install Ubuntu along side of it (dual boot). I have a 2TB disk that is just under half full. This is not a primary disk, it is all backup. When I am booted into Centos the disk is /dev/sdc, and is just a single partition (no numbers after /dev/sdc). I created a bootable usb with Ubuntu 18.04 on it, booted from the usb, and the disk was recognized in that system as /dev/sda. I ran gparted, and told it to shrink the partition by ~400GB:

gparted screenshot 1

This looked correct to me, so I went ahead and applied the changes. It finished without issue. However, when it was done there was still only 1 partition, with the unallocated space inside of it, rather than the partition itself shrinking. There's even an alert icon that when I click on it tells me that there is 390.63GB within the partition asking me if I want to grow it:

gparted screenshot 2

I know that I could, if I had enough disk space elsewhere, copy the data over and repartition this drive from scratch. However, I don't actually have enough space to do that, and things are pretty tight inside the box right now with 5 drives. Is there any way to split this drive into multiple partitions without going that route?

Not sure if this is relevant, but when I was still booted into Ubuntu the first time I did this I ran Check on it from gparted, and when it did that it automatically resized it back. I don't know if that means that it detected the wrong size as being an actual error, or if it is normal for gparted to just make use of extra space like that when you run check. I re-ran the resizing operation again before booting back into CentOS and it still currently looks like the second screenshot, and df says that the partition is 1.5TB with 882GB used and 494G available.

2 Answers 2


When I am booted into Centos the disk is /dev/sdc, and is just a single partition (no numbers after /dev/sdc).

/dev/sdc is not a partition, it's the disk itself which not partitioned, you have an ext4 filesystem directly on the disk without a partition table so you can't add partitions to your disk.

By shrinking the drive you really only shrunk the filesystem which is why you see the free space inside of it.

I know that I could, if I had enough disk space elsewhere, copy the data over and repartition this drive from scratch

This is unfortunately only thing you can do now, you can't add a partition table to the disk, because there is not enough space for it, you'd need to move the filesystem few sectors forward to make space for the pt which is in theory possible but very complicated and with high risk of losing your data.


The problem

You don't have partitions. The file system exists on the disk but with no partitions. So the file system was shrunk, but there is no partition to shrink.


I have no idea if there a tools to just do this. However.

It can be done. I did it years ago (before the nice tools existed). The partition table is just a few blocks at the start of the disk. Therefore,

  • Make a backup (just in case).
  • Move the file-system up a bit to make room for the partition table (if needed: if it is not already offset from the start).
  • Create a partition table, with a definition of one partition, at the location of your file-system.
  • Force the OS to read and interpret the partition table.

Now you can use tools to add new partitions, and file-systems.

  • "Make a backup (just in case)." - If I had room to do that I could just reformat the disk with partitions. Thank you though. Feb 6, 2021 at 22:07
  • I put that line in so that it is not by fault. I would back it up to some where because one day the device will fail. But I notice that you say it is all backup, so you already have a backup (the primary). Feb 6, 2021 at 22:15
  • not exactly, it's a backup of another disk that I no longer have. I included that to highlight that it's not the primary disk. Losing the data would still be sub-optimal, just not as catastrophic as losing my primary or one of my other storage disks. Feb 6, 2021 at 22:20
  • 1
    You will have to do the risk-benefit analysis for your self. Feb 6, 2021 at 22:23

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