How recovery SSH keys on VPS in Oracle Cloud

0. Create new instance with SSH keys.

1. Stop current instance and go to the 'Boot volume' -> Detach current Boot Volume.

3. Go to the Second instance and go to the 'Attach block volunes' and Attach Boot Volume of first instance.

4. Connect through SSH, sudo su and run commands from 'iSCSI commands & information' ('Attached Blocked volume').

5. Check new Volumes:

lsblk
fdisk -l /dev/sdb

6. Mount new Volume:

sudo mount -t ext4 /dev/sdb1 /mnt

7. Check mounted volume:

df -h

8. Open /user/.ssh/authorized_keys and update SSH-keys or add new. Save.

9. Unmount volume:

sudo umount /mnt

10. Detach iSCSI by runing detach commands from 'iSCSI commands & information' ('Attached Blocked volume').

11. exit SSH

12. Detach volume in Oracle Instance Details view -> Attached Block Volumes

13. Go to the first instance -> 'Boot Volume' and attach again native Volume.

14. Start instance.

15. Connect via new SSH keys

PROFIT.

Reference: https://blogs.oracle.com/cloud-infrastructure/post/recovering-opc-user-ssh-key-on-oracle-cloud-infrastructure