There should be an empty line after the title tag.

s/constain/contains/

s/troubleshot/troubleshoot/

You can move the closing <para> up right behind the "guest." part. textproc/igor will tell you about these.

You can start writing right after <para>, no need for a line break here.

s/troubleshootting/troubleshooting/

Extra space after a sentence stop. textproc/igor will also find and tell you about those occurances (what a snitch). ;-)

The "in order" can be left out.

s/reate/rate/

s/guest/guests/

I'd add: "To activate verbose booting, run this command:"

s/this/these/
s/helps/help/

s/diagnostic/diagnostics/ (or even analysis?)

The "creation" should be capitalized. textproc/igor will remind you of that. Only a few words in title tags are lowercase like "the", "a", or "of".

I'd also add <literal> tags to this instance of xl.

Sentence stop missing here. Not sure if textproc/igor is looking for those...

you can also use the &os; placeholder here (and in the next two lines) if you like, but it's optional.

I'd add a sentence stop after the </filename> here and start a new sentence: Both log files can contain useful information for debugging.

I've left this as 'freebsd', since the guest name in the example config name uses 'freebsd' instead of &os;