martin@duskware.de wrote:

> Writing boot block
> installboot: Writing `/dev/rsd0a': Read-only file system
> installboot: Set bootstrap operation failed

You can't open a raw device if the corresponding block device is mounted.
If sd0a is started at the top of the disk, using sd0c does the trick.

> I then rebooted, and apparently the new bootstrap (both primary and secondary)
> has been installed, and they worked fine.
> 
> So, did I do something wrong, or is this just a bogus error message from
> installboot?

Hmm, no idea.
---
Izumi Tsutsui