Useful tip on nsupdate -- readline support.

[Warren Kumari]

On Tue, Jun 11, 2019 at 10:59 AM Mukund Sivaraman <muks at mukund.org> wrote:
>
> On Tue, Jun 11, 2019 at 10:03:30AM -0400, Warren Kumari wrote:
> > Hi there all,
> >
> > I manually use nsupdate to make some changes to some of my zones -
> > most recently I had to add a bunch of reverse DNS records. These are
> > all very similar - the first octet changes, and then the target name
> > changes. Unfortuniatly nsupdate doesn't support readline, and so the
> > obvious "press up arrow, edit previous line, press enter" doesn't
> > work, and so I end up entering one line, copying that into an editor,
> > making changes, pasting, making changes, etc.
> >
> > I just stumbled across this --
> > https://dnsworkshop.de/nsupdate-history.html by Carsten Strotmann
> >
> > Basically, uses rlwrap to wrap readline support into nsupdate - you
> > just call `rlwrap nsupdate` and magically nsupdate now supports
> > editing.
> >
> > 'tis a simple trick, but removes much annoyance.
>
> nsupdate has built-in readline support (when it finds it during build).
> (Though, for for some reason, the nsupdate that ships with Fedora
> doesn't seem to be linking to readline.)
>

Yup - Jim Reid also just sent me mail mentioning this, and looking in
the nsupdate code I find:

#if defined(HAVE_READLINE)
#include <readline/readline.h>
#include <readline/history.h>
#endif

I build from source, and apparently I need to add '--with-readline' to
my configure invocation.


> On that note, buyer beware. A warning to all redistributors who
> commercially repackage BIND with modifications (whether with blessing
> from ISC or not):
>
> * readline is GPL, and so you'll link your code to GPL if you link to it
>   (which can be esp. bad for you if you modify libisc, libdns,
>   etc. also). It's best to either remove readline from such build
>   environments (libedit may be a suitable drop-in replacement), or
>   configure without it, or patch out the code.
>
>   There is some interesting GPL license enforcement history with readline:
>
>   https://en.wikipedia.org/wiki/GNU_Readline#Choice_of_the_GPL_as_GNU_Readline's_license
>   https://gitlab.com/gnu-clisp/clisp/blob/master/doc/Why-CLISP-is-under-GPL
>
> * libcap (POSIX capablities) is GPL similarly. An alternative is
>   libcap-ng which is LGPLv2+, but it has a different API.
>
> I think these are the only two libraries that are copyleft vs. BIND's
> ISC (before) and MPL2 (now) licenses, and because they're GPL, your work
> will be covered by GPL if you link against them.
>
> This is usually not bad for the general public (and good for free
> software), but if you're a commercial re-distributor of BIND and are
> linking to GPL, good luck. I'm sure you'll even miss seeing this
> thread. :)

Indeed :-)
W

>
>                 Mukund



-- 
I don't think the execution is relevant when it was obviously a bad
idea in the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair
of pants.
   ---maf