Rebooting, Deleting, Rebuilding, Resizing

Rebuilding

You can Rebuild an instance. This means that your instance will retain its flavour, volume attachments and IP-address, but it will have a new image applied to it. The astute observer will start to recognise a bit of a pattern; something to do with the Instances page on your Nectar Dashboard and performing some sort of action on your instance from the Action Menu.

Warning The Rebuild action erases all data on your instance primary and ephemeral drive (if it has one), including installed software, configuration settings and user data.

Manage your data Before rebuilding your instance, you should manage your data. You should store your valuable data on persistent storage, e.g. Nectar Volume Storage or File Shares, or your institution storage options or your local machine.

Action Menu Rebuild

Rebuild Dialog

Rebuild Status

Warning: Remote Host Identification Changed
If you use Rebuild and then reconnect to your instance using ssh you will typically receive a REMOTE HOST IDENTIFICATION HAS CHANGED!-warning. This is expected behaviour after a Rebuild as ssh detects a materially different computer using an old IP-address.

When you receive the REMOTE HOST IDENTIFICATION HAS CHANGED!-warning ssh typically suggests how you can resolve this situation, but this depends on a combination of ssh-client, terminal software and operating system and possibly your computer’s mood. ssh keeps track of computers that you have previously connected to using the .ssh/known_hosts-file. If a computer that ssh has previously connected to looks materially different now than it did in the past, ssh will refuse to connect (or display a stern warning). If you have just rebuilt your VM, then your VM will look materially different, and ssh will throw this warning.

To resolve this situation, and allow ssh to connect to your rebuilt instance, you will have to use a command to forget the old instance’ fingerprint. You can do this as below (remember to fill in the ip-address of your instance):

$ ssh-keygen -R [your-ip-address]

To make things easy as well as secure, ssh typically includes these instructions in its warning message.