Why is the device busy while extending the partition?

Question

linux

After fdisk they write to me:

Re-reading the partition table failed device or resource busy

partrobe - did not help.
mount says:
/dev/xvda1 on /
I don't know if this is normal or not. But umount /dev/xvda1 doesn't work.
Thanks everyone for the replies.

Answer 1

Since this is xvda1, then it is likely that this system partition, which is already mounted in /.
To repartition the system disk, you need to boot from another media.