docs/logging_and_backgrounding.txt: new mini-doc

dnsd: remove statics, remove nerly-useless SIGINT handler
crond: correct more of logfile to 0666 (as usual, umask allows
 user to remove unwanted bits).
nameif: print errors to stderr too, not just to syslog

function                                             old     new   delta
udhcp_read_interface                                 308     306      -2
ttl                                                    4       -      -4
fileconf                                               4       -      -4
dnsentry                                               4       -      -4
interrupt                                             19       -     -19
dnsd_main                                           1463    1394     -69
------------------------------------------------------------------------------
(add/remove: 0/4 grow/shrink: 0/2 up/down: 0/-102)           Total: -102 bytes
   text    data     bss     dec     hex filename
 808161     476    7864  816501   c7575 busybox_old
 807994     468    7856  816318   c74be busybox_unstripped

1 files changed, 89 insertions, 0 deletions

diff --git a/docs/logging_and_backgrounding.txt b/docs/logging_and_backgrounding.txt
new file mode 100644
index 000000000..39f015883
--- /dev/null
+++ b/docs/logging_and_backgrounding.txt
@@ -0,0 +1,89 @@
+        Logging and backgrounding
+
+By default, bb_[p]error_msg[_and_die] messages go to stderr,
+and of course, usually applets do not auto-background. :)
+
+Historically, daemons and inetd services are different.
+
+Busybox is trying to provide compatible behavior, thus if an applet
+is emulating an existing utility, it should mimic it. If utility
+auto-backgrounds itself, busybox applet should do the same.
+If utility normally logs to syslog, busybox applet should do
+the same too.
+
+However, busybox should not needlessly restrict the freedom
+of the users. And users have different needs and different preferences.
+Some might like logging everything from daemons to syslog.
+Others prefer running stuff under runsv/svlogd and thus would like
+logging to stderr and no daemonization.
+
+To help with that, busybox applets should have options to override
+default behavior, whatever that is for a given applet.
+
+
+Current sutiation is a bit of a mess:
+
+acpid - auto-backgrounds unless -d
+crond - auto-backgrounds unless -f, logs to syslog unless -d or -L.
+    option -d logs to stderr, -L FILE logs to FILE
+devfsd - (obsolete)
+dnsd - option -d makes it auto-background and log to syslog
+fakeidentd - inetd service. Auto-backgrounds and logs to syslog
+    if no -f and no -i and no -w (-i is "inetd service" flag,
+    -w is "inetd-wait service" flag)
+ftpd - inetd service. Logs to syslog always, with -v logs to strerr too
+httpd - auto-backgrounds unless -f or -i
+    (-i is "inetd service" flag)
+inetd - auto-backgrounds unless -f, logs to syslog unless -e
+klogd - auto-backgrounds unless -n
+syslogd - auto-backgrounds unless -n
+telnetd - auto-backgrounds unless -f or -i
+    (-i is "inetd service" flag)
+udhcpc - auto-backgrounds unless -f after lease is obtained,
+    option -b makes it background sooner (when lease attempt
+    fails and retries start),
+    after backgrounding it stops logging to stderr;
+    logs to stderr, but option -S makes it log *also* to syslog
+udhcpd - auto-backgrounds and do not log to stderr unless -f,
+    otherwise logs to stderr, but option -S makes it log *also* to syslog
+zcip - auto-backgrounds and logs *also* to syslog unless -f
+
+miscutils/crond.c:            logmode = LOGMODE_SYSLOG;
+networking/dnsd.c:            logmode = LOGMODE_SYSLOG;
+networking/ftpd.c:            logmode = LOGMODE_SYSLOG;
+networking/ftpd.c:            logmode |= LOGMODE_SYSLOG;
+networking/inetd.c:           logmode = LOGMODE_SYSLOG;
+networking/isrv_identd.c:     logmode = LOGMODE_SYSLOG;
+networking/telnetd.c:         logmode = LOGMODE_SYSLOG;
+networking/udhcp/dhcpc.c:     logmode = LOGMODE_NONE;
+networking/udhcp/dhcpc.c:     logmode |= LOGMODE_SYSLOG;
+networking/udhcp/dhcpc.c:     logmode &= ~LOGMODE_STDIO;
+networking/udhcp/dhcpd.c:     logmode = LOGMODE_NONE;
+networking/udhcp/dhcpd.c:     logmode |= LOGMODE_SYSLOG;
+networking/zcip.c:            logmode |= LOGMODE_SYSLOG;
+
+
+These daemons seem to never auto-background/log to syslog:
+
+lpd - inetd service. Has nothing to log so far, though
+dhcprelay - standard behavior
+inotifyd - standard behavior
+runsv - standard behavior
+runsvdir - standard behavior
+svlogd - standard behavior
+tcpsvd, udpsvd - standard behavior
+tftpd - standard behavior
+
+
+Non-daemons (seems to be use syslog for a good reason):
+
+networking/nameif.c:          logmode |= LOGMODE_SYSLOG;
+loginutils/chpasswd.c:        logmode = LOGMODE_BOTH;
+loginutils/chpasswd.c:        logmode = LOGMODE_STDIO;
+loginutils/getty.c:           logmode = LOGMODE_BOTH;
+loginutils/getty.c:           logmode = LOGMODE_NONE;
+loginutils/passwd.c:          logmode = LOGMODE_STDIO;
+loginutils/passwd.c:          logmode = LOGMODE_BOTH;
+loginutils/sulogin.c:         logmode = LOGMODE_SYSLOG; (used if stdio isn't a tty)
+loginutils/sulogin.c:         logmode = LOGMODE_BOTH;
+util-linux/mount.c:           logmode = LOGMODE_SYSLOG; (used in a backgrounded NFS mount helper)