How can I check that my disk repartitioning has been completed safely? [closed]

Background: My desktop computer came with an SSD drive with a working Windows 10 install. I installed Linux (Mint 18.3 w/ Cinnamon) into a new extended partition with the default boot, swap, main partitions. For some reason Windows failed to boot, but as I never use Windows I haven't worried about it.

Recently I've been running short of disk space, so the obvious solution was to eliminate the Windows partition to reclaim space. I opened up the Disks tool and deleted the Windows partition, expecting to be able to the resize the extended partition. Instead, the extended partition is now showing as empty, and there is empty space both before and after the extended partition. In effect, it looks like the disk has been wiped.

However, my filesystem remains mounted and I appear to still have normal access to all my files. df -h reports the size and usage that I expect to see.

In other words, I don't know whether or not my install is safe - is it only working now because there was an active mount when Disks clobbered the partitions? Or is Disks misreading something and in fact it's all safe? As you can imagine, I'm not keen to reboot and find out!

Solution 1:

You'll need to boot from a Live USB to resize your main partition. You cannot, at least easily and as far as I know at all, resize a mounted partition. If you are able to use the system then it has not been wiped.

And please remember to backup your data before resizing.