Here is a tutorial that will come handy one day, in the moment of panic – How to Recover an Unreachable Linux Instance. It has plenty of screenshots and shows each step in detail.
TL;DR version:
- Start a new instance (or pick one from the existing ones).
- Stop the broken instance.
- Detach the volume from the broken instance.
- Attach the volume to the new/existing instance as additional disk.
- Troubleshoot and fix the problem.
- Detach the volume from the new/existing instance.
- Attach the volume to the broken instance.
- Start the new instance.
- Get rid of the useless new instance, if you didn’t reuse the existing one for the troubleshooting and fixing process.
- ???
- PROFIT!