I recently attempted to enable FileVault on macOS Sierra. I clicked the restart button, but on reboot rather than starting to encrypt the disk it simply displayed the prohibited sign. Now I can't boot to my Sierra drive in single-user mode either.
My Recovery paritions (one for Sierra and one from an older El Capitan install whose main partition no longer exists) are both displaying the same issue, no booting to recovery in general or in safe mode. I need help, I had a lot of code store on the Sierra partition, but I never made backups of some of it, and the backups I have are several weeks old. I don't have the recovery key, it is in a file on the now dysfunctional recovery disk, so I need to know, is there any way to salvage the install from a macOS install usb?
If so is Mavericks a new enough version to do so from? Can I simply decrypt my Sierra partition from inside of it or would I require at least a Sierra installer to do so, and if I can't decrypt it from an installer, would it be safe to install Mavericks over Sierra, or to a different disk, extract my personal/company projects from it and simply re-upgrade once I had it working again in general. Again I need help, and I would rather not have to wipe and lose all of that data.
UPDATE: It seems the Mavericks installer can't load drivers on boot, and I don't know of another way to access the filesystem. If it turned out the disk didn't get encrypted would it be possible to boot a live copy of linux, mount the disk and disable FileVault from there? If so how would I disable FileVault?