Theoretical situation regarding lost ssh keys

This has not happened to me, yet.

But let's assume the following scenario:

I copy my public key to the server, and then disable password authentication for ssh. Then, for some unknown reason, the public key on the server gets corrupted, and I can no longer login because I have turned off password authentication.

What are my options for regaining access to that server?

Solution 1:

Unless you have either console access or a another user account that can still log in: none.

Solution 2:

If you assume random data can become corrupted, there are many many other things to worry about that would make login impossible, including but not limited to: your shell, the libc, the sshd binary or any of its dynamically linked libraries, the structure of the fs itself...

You can protect against all of them at once by using either a checksumming filesystem with redundant disks (like zfs, or btrfs when it gets the relevant features), or maybe something like raid6, which wastes two disks for redundancy but can heal silent corruption on a single disk.