As noted in my comments to eyoung100 (EDIT: in a now-deleted answer), I don't see this problem with Debian's open-scsi 2.1.3-5 package. Also, there are no font selection escape sequences (or requests) on line 498 of my copy of that document, so you are almost certainly using another version.
My copy formats without warnings:
$ nroff -ww -man -z ./doc/iscsiadm.8
(I used -ww to turn on all warnings and -z to suppress formatted output, since all I am interested in are diagnostic messages.)
I do see, at line 503 of my copy of the doc/iscsiadm.8 file, the following:
like you would in node mode, run \fIiscsiadm \-m fw\fR.
If I delete the capital I, I get the following.
$ nroff -ww -man -z ./doc/iscsiadm.8
troff:./doc/iscsiadm.8:503: warning: cannot select font 'i'
I therefore think something similar is happening with your copy.
You might try this:
$ zgrep '\\fi' $(man -w iscsiadm)
That should tell you if the page has the error I suspect.
One might wonder why the error happens. It is due to the syntax of the font selection escape sequence \f. Here's how groff(7) summarizes it.
\fP Select previous font mounting position (abstract style or
font); same as “.ft” or “.ft P”.
\fF Select font mounting position, abstract style, or font with
one‐character name or one‐digit position F. F cannot be P.
\f(ft Select font mounting position, abstract style, or font with
two‐character name or two‐digit position ft.
\f[font]
Select font mounting position, abstract style, or font with
arbitrarily long name or position font. font cannot be P.
\f[] Select previous font mounting position (abstract style or
font).
The square-bracket forms are GNU troff extensions to the AT&T troff language. (They might actually originate in SoftQuad troff, a now nearly forgotten descendant of AT&T's Documenter's Workbench 2.0 troff.)
So when you have \f followed by something other than an opening parenthesis ( or opening square bracket [, the next character is interpreted as the name of the font to be selected. (It could also be a single-digit font mounting position, but this usage is vanishingly rare in man(7) pages--fortunately.)
As far as groff is concerned, terminals support only four font names: R, I, B, and BI; the grotty(1) man page says more. Attempting to select any other font name will fail; like much else in Unix, *roff font names are case-sensitive. groff 1.23.0 started issuing diagnostics upon font selection failure in many more cases than earlier versions of groff did.
man iscsiadm 2>/tmp/test1.txt | grep "aia", thenman iscsiadm 2>/tmp/test2.txt | grep "ia". In both cases, you should no longer see the error, because the error messages are redirected to a text file; if you still see it, something very strange is happening. Then compare the files/tmp/test1.txtand/tmp/test2.txt. Are they in fact both the same, or different? (Please edit your question to add this information; leave a comment only if you have a problem doing what was asked.) I'll write a more complete answer once I'll know the results of this test.iscsiadmman page that always triggers the error, but it doesn't come visible when grepping foriaoraibecause the partial output from the man page formatter process overwrites the error message on screen. But when the man page output is further constrained bygrep "aia", the error won't get overwritten on screen and can be seen. The test suggested in my first comment should prove that the error is not related togrepbut to themancommand and its man page formatting process chain.grep, and then unpack the rest of the relationship betweenmanandtroffonce that was confirmed. You drilled right down into the root cause, but as a result, unless the asker reads it very carefully or already knows a bit about howmanworks, your answer standing alone could have left the asker thinking "well and good, but how is this related to my error message fromgrep"?