Provided by: rsyslog_8.16.0-1ubuntu3_i386 bug


       rsyslogd - reliable and extended syslogd


       rsyslogd  [  -d ] [ -D ] [ -f config file ] [ -i pid file ] [ -n ] [ -N
       level ] [ -C ] [ -v ]


       Rsyslogd is a system utility providing  support  for  message  logging.
       Support  of  both internet and unix domain sockets enables this utility
       to support both local and remote logging.

       Note that this version of rsyslog ships with extensive documentation in
       html  format.   This is provided in the ./doc subdirectory and probably
       in a separate package if you installed rsyslog via a packaging  system.
       To  use  rsyslog's  advanced  features,  you  need  to look at the html
       documentation, because the man  pages  only  covers  basic  aspects  of
       operation.    For   details   and   configuration   examples,  see  the
       rsyslog.conf  (5)  man   page   and   the   online   documentation   at

       Rsyslogd(8)  is  derived  from  the  sysklogd  package which in turn is
       derived from the stock BSD sources.

       Rsyslogd provides a kind of logging  that  many  modern  programs  use.
       Every  logged  message  contains  at least a time and a hostname field,
       normally a program name field, too, but that depends on how trusty  the
       logging  program  is.  The  rsyslog package supports free definition of
       output formats via templates. It also supports precise  timestamps  and
       writing  directly  to  databases. If the database option is used, tools
       like phpLogCon can be used to view the log data.

       While the rsyslogd sources have been heavily modified a couple of notes
       are  in  order.   First  of  all there has been a systematic attempt to
       ensure that rsyslogd follows its default,  standard  BSD  behavior.  Of
       course,  some  configuration  file  changes  are  necessary in order to
       support the template system. However, rsyslogd should be able to use  a
       standard  syslog.conf  and  act  like the original syslogd. However, an
       original syslogd  will  not  work  correctly  with  a  rsyslog-enhanced
       configuration file. At best, it will generate funny looking file names.
       The second important concept to note is that this version  of  rsyslogd
       interacts  transparently  with  the  version  of  syslog  found  in the
       standard  libraries.   If  a  binary  linked  to  the  standard  shared
       libraries  fails  to function correctly we would like an example of the
       anomalous behavior.

       The main configuration file /etc/rsyslog.conf or an  alternative  file,
       given  with  the  -f  option, is read at startup.  Any lines that begin
       with the hash mark (``#'') and empty lines are ignored.   If  an  error
       occurs  during  parsing  the  error  element is ignored. It is tried to
       parse the rest of the line.


       -D     Runs the Bison config parser in debug mode. This may  help  when
              hard  to  find  syntax errors are reported. Please note that the
              output generated is  deeply  technical  and  orignally  targeted
              towards developers.

       -d     Turns  on  debug  mode.  See  the  DEBUGGING  section  for  more

       -f config file
              Specify   an   alternative   configuration   file   instead   of
              /etc/rsyslog.conf, which is the default.

       -i pid file
              Specify  an  alternative  pid  file  instead of the default one.
              This option must be  used  if  multiple  instances  of  rsyslogd
              should run on a single machine.

       -n     Avoid  auto-backgrounding.   This  is  needed  especially if the
              rsyslogd is started and controlled by init(8).

       -N  level
              Do a coNfig check. Do  NOT  run  in  regular  mode,  just  check
              configuration  file correctness.  This option is meant to verify
              a  config  file.  To  do  so,  run  rsyslogd  interactively   in
              foreground, specifying -f <config-file> and -N level.  The level
              argument modifies behaviour. Currently, 0 is  the  same  as  not
              specifying  the  -N  option at all (so this makes limited sense)
              and 1 actually activates the code.  Later,  higher  levels  will
              mean  more  verbosity  (this is a forward-compatibility option).
              rsyslogd is started and controlled by init(8).

       -C     This prevents rsyslogd from changing to the root directory. This
              is  almost  never a good idea in production use. This option was
              introduced in support of the internal testbed.

       -v     Print version and exit.


       Rsyslogd reacts to a set of signals.  You may easily send a  signal  to
       rsyslogd using the following:

              kill -SIGNAL $(cat /var/run/

       Note  that  -SIGNAL  must  be  replaced  with the actual signal you are
       trying to send, e.g. with HUP. So it then becomes:

              kill -HUP $(cat /var/run/

       HUP    This lets rsyslogd perform close all open files.

       TERM ,  INT ,  QUIT
              Rsyslogd will die.

       USR1   Switch debugging on/off.   This  option  can  only  be  used  if
              rsyslogd is started with the -d debug option.

       CHLD   Wait for childs if some were born, because of wall'ing messages.


       There  is the potential for the rsyslogd daemon to be used as a conduit
       for a denial of service attack.  A rogue program(mer) could very easily
       flood  the  rsyslogd  daemon  with syslog messages resulting in the log
       files consuming all the remaining space on the filesystem.   Activating
       logging  over the inet domain sockets will of course expose a system to
       risks outside of programs or individuals on the local machine.

       There are a number of methods of protecting a machine:

       1.     Implement kernel firewalling to limit which  hosts  or  networks
              have access to the 514/UDP socket.

       2.     Logging  can  be  directed to an isolated or non-root filesystem
              which, if filled, will not impair the machine.

       3.     The ext2 filesystem can be used which can be configured to limit
              a  certain  percentage  of  a  filesystem to usage by root only.
              NOTE that this will require rsyslogd to be  run  as  a  non-root
              process.   ALSO  NOTE  that  this  will  prevent usage of remote
              logging on the default port since rsyslogd  will  be  unable  to
              bind to the 514/UDP socket.

       4.     Disabling  inet  domain  sockets  will  limit  risk to the local

   Message replay and spoofing
       If remote logging is  enabled,  messages  can  easily  be  spoofed  and
       replayed.   As  the messages are transmitted in clear-text, an attacker
       might use the information  obtained  from  the  packets  for  malicious
       things.  Also,  an  attacker  might replay recorded messages or spoof a
       sender's IP address, which could lead to a wrong perception  of  system
       activity.  These  can  be prevented by using GSS-API authentication and
       encryption. Be sure to  think  about  syslog  network  security  before
       enabling it.


       When  debugging  is  turned  on  using the -d option, rsyslogd produces
       debugging  information  according  to  the  RSYSLOG_DEBUG   environment
       variable  and  the  signals  received.  When  run  in  foreground,  the
       information is written to stdout. An  additional  output  file  can  be
       specified using the RSYSLOG_DEBUGLOG environment variable.


              Configuration  file for rsyslogd.  See rsyslog.conf(5) for exact
              The Unix domain socket to from where local syslog  messages  are
              The file containing the process id of rsyslogd.
              Default  directory for rsyslogd modules. The prefix is specified
              during compilation (e.g. /usr/local).


              Controls runtime debug support. It  contains  an  option  string
              with the following options possible (all are case insensitive):

              Debug  Turns   on   debugging  and  prevents  forking.  This  is
                     processed  earlier  in  the  startup  than  command  line
                     options  (i.e.  -d) and as such enables earlier debugging
                     output. Mutually exclusive with DebugOnDemand.
                     Enables debugging but turns off debug output. The  output
                     can  be  toggled  by  sending SIGUSR1. Mutually exclusive
                     with Debug.
                     Print out the logical flow  of  functions  (entering  and
                     exiting them)
                     Specifies  which  files  to trace LogFuncFlow. If not set
                     (the default), a LogFuncFlow trace is  provided  for  all
                     files.  Set  to limit it to the files specified.FileTrace
                     may be specified multiple  times,  one  file  each  (e.g.
                     export      RSYSLOG_DEBUG="LogFuncFlow     FileTrace=vm.c
                     Print the content of the debug function database whenever
                     debug information is printed (e.g. abort case)!
                     Print  all  debug information immediately before rsyslogd
                     exits (currently not implemented!)
                     Print mutex action as  it  happens.  Useful  for  finding
                     deadlocks and such.
                     Do  not  prefix log lines with a timestamp (default is to
                     do that).
                     Do not emit debug messages to stdout. If RSYSLOG_DEBUGLOG
                     is  not  set, this means no messages will be displayed at
              Help   Display a very short list of commands - hopefully a  life
                     saver if you can't access the documentation...

              If  set,  writes (almost) all debug message to the specified log
              file in addition to stdout.
              Provides the default directory in which loadable modules reside.


       Please review the file BUGS for up-to-date information  on  known  bugs
       and annoyances.

Further Information

       Please  visit  for  additional information,
       tutorials and a support forum.


       rsyslog.conf(5),   logger(1),   syslog(2),   syslog(3),    services(5),


       rsyslogd is derived from sysklogd sources, which in turn was taken from
       the    BSD    sources.    Special    thanks    to    Greg     Wettstein
       (  and  Martin  Schulze  ( for the
       fine sysklogd package.

       Rainer Gerhards
       Adiscon GmbH
       Grossrinderfeld, Germany