Repairing a mount configuration problem

[Petrus de Calguarium]

I recently made some changes with the partitions on my system and neglected to update fstab. As the system booted, a message appeared, stating I could:

1. type Ctrl-D to continue (I tried that, and it caused the computer to reboot and stop anew at the same problem - not very useful); or

2. type the root password to fix the problem.

Upon trying the second method, the system logged me in, but I was unable to fix anything because the partitions were mounted read only. This is also not useful.

How am I supposed to fix the problem (I knew exactly what it was) when I am barred from changing anything?