LVM went into read-only file system mode. How to find out the reason?

Question

I got the same error as Read-only root file system - ext3 error?.

There is no error log in /var/log/message. Because root (/) is read-only, no log can be recorded.

How can I find out the root cause?

Answer 1

Chances are very good the reason got logged on the ring-buffer. dmesg will probably have the error that would have been logged.