Re: isc dhcpd won't log to stdout/stderr

[Charlie Brady <charlieb-supervision@budge.apana.org.au>]

On Thu, 8 Dec 2005, Dean Hall wrote:

> I'm trying to get dhcpd (3.0.1) supervised by runsv on Gentoo Linux, and 
> though dhcpd's man page says that it will log to STDERR with the "-d" flag, 
> and though I'm using that flag when I run it, all logs still go straight to 
> syslog. I even commented the "log-facility" directive in dhcpd.conf just in 
> case. Has anyone got this version to log to STDERR successfully?

I see the same as you. Looks like a bug in dhcpd to me.

<checks>

OK, here's the story.

Don't use "-d -q", just use "-d". That'll get you stderr logging, but as 
well as syslog, not instead of.

If you don't want syslog, compile with -DDEBUG (although that might make 
other changes you don't want - I haven't checked what else it does).

Here's log_info(). As you can see, it logs to syslog and then to stderr 
iff log_perror is non-zero:

omapip/errwarn.c
int log_info (const char *fmt, ...)
{
   va_list list;

   do_percentm (fbuf, fmt);

   /* %Audit% This is log output. %2004.06.17,Safe%
    * If we truncate we hope the user can get a hint from the log.
    */
   va_start (list, fmt);
   vsnprintf (mbuf, sizeof mbuf, fbuf, list);
   va_end (list);

#ifndef DEBUG
   syslog (log_priority | LOG_INFO, "%s", mbuf);
#endif

   if (log_perror) {
           write (2, mbuf, strlen (mbuf));
           write (2, "\n", 1);
   }

   return 0;
}

server/dhcpd.c:

...
                 } else if (!strcmp (argv [i], "-f")) {
#ifndef DEBUG
                         daemon = 0;
#endif
                 } else if (!strcmp (argv [i], "-d")) {
#ifndef DEBUG
                         daemon = 0;
#endif
                         log_perror = -1;
                 } else if (!strcmp (argv [i], "-s")) {
...
                 } else if (!strcmp (argv [i], "-q")) {
                         quiet = 1;
                         quiet_interface_discovery = 1;
                 } else if (!strcmp (argv [i], "--version")) {
...
         if (!quiet) {
                 log_info ("%s %s", message, DHCP_VERSION);
                 log_info (copyright);
                 log_info (arr);
                 log_info (url);
         } else {
                 quiet = 0;
                 log_perror = 0;
         }
...
         /* If we were requested to log to stdout on the command line,
            keep doing so; otherwise, stop. */
         if (log_perror == -1)
                 log_perror = 1;
         else
                 log_perror = 0;
...

So, -q clobbers the effect of -d on logging. And -f isn't needed if you 
use -d. So just use -d, and put up with logging to syslog, or compile with 
-DDEBUG, or patch the code.