OVH VPS upgrade/disk resize:

1. reboot from live-cd
2. lsblk
3. umount /dev/vdb1
4. e2fsck -yf /dev/vdb1
5. fdisk -u /dev/vdb
6. Command (m for help): p
7. Command (m for help): d
8. Command (m for help): n
9. Select (default p): p
10. Partition number (1-4, default 1): 1
11. Command (m for help): a
13. Command (m for help): w
14. dumpe2fs /dev/vdb1 | grep superblock
15. fsck -b 32768 /dev/vdb1 (if error present use 15.1)
15.1 e2fsck -yf /dev/vdb1
16. mount /dev/vdb1 /mnt
17. df -h
18. disable live-cd and reboot

Original OVH post