I have these lines in /boot/loader.conf in order to enable a sometimes-installed serial console device: boot_multicons="YES" boot_serial="YES" comconsole_speed="19200" console="comconsole,vidconsole" A side effect of these lines is that entering single-user mode produces a prompt only on the external console. This was extremely confusing when attempting to boot single-user, as all messages prior to the single-user prompt are produced on the vid terminal (and on the external console), however at the moment that single-user mode is entered, the mirroring ceases. While it is now clear what happened, the effect is that single-user mode appears to be unavailable. I have no /boot.config file that would indicate which console is meant to be used for messages. Fix: I would suggest adding some text to the handbook page "Setting up the Serial Console" http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/serialconsole-setup.html#serialconsole-loader Currently, these page makes no comment regarding single-user mode whatsoever. Informing the user that configuring the console may well have repercussions on entry to single-user mode will lessen confusion in the future. I would therefore suggest adding the following text into section 26.6.6 "Setting up the Console from the Boot Loader", subsection 26.6.6.1 "Setting Up the Serial Console": Note that entry to single-user mode will only honour input on one console, even if multiple consoles are indicated using the <tt>console</tt> boot option. Care must be taken that the first named console is available to the system manager entering single-user mode. I will note that the first sentence in this section "The boot loader and the kernel to use the serial console can be specified by writing one line in /boot/loader.conf" seems very poorly written -- I do not understand what this line is attempting to say. Additionally, there is already a section "26.6.7 Caveats"; a note here indicating possible effects on single-user boot would probably not go amiss. How-To-Repeat: Add these lines to /boot/loader.conf, attempt to boot single user.
For bugs matching the following criteria: Status: In Progress Changed: (is less than) 2014-06-01 Reset to default assignee and clear in-progress tags. Mail being skipped
Triage: * remove the summary line tag * … <https://wiki.freebsd.org/Bugzilla> ---- Whilst here, speeding through comment #0: > … already a section "… Caveats"; … The word caveat no longer appears in this chapter of the book.
In the nine years since I reported this bug and suggested the included text, the entire section on consoles has been rewritten. I would still suggest that some comment as to how single-user mode is affected by setting up multiple consoles be included in the handbook, as this is still not very clear in the console configuration section: https://github.com/freebsd/freebsd-doc/blob/main/documentation/content/en/books/handbook/serialcomms/_index.adoc#serialconsole-setup My guess is that single-user mode ends up on the console indicated with -h in /boot.config (if present), however with the addition of dual console mode I have no idea whether this results in two separate consoles from which one can log in to single-user mode. I no longer have the device I was using as an external serial console however, so can no longer test whatever advice is being given.