Provided by: rsyslog_8.2208.0-1ubuntu2_amd64 bug


       rsyslogd - reliable and extended syslogd


       rsyslogd  [  -d  ]  [  -D  ]  [  -f config file ] [ -i pid file ] [ -n ] [ -N level ] [ -o
       fullconf ] [ -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

       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 information.

       -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. To disable
              writing a pid file, use the reserved name "NONE" (all upper case!), so "-iNONE".

       -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

       -o  fullconf
              Generates  a  consolidated  config  file  fullconf  that  contains all of rsyslog's
              configuration in a single file. Include  files  are  exploded  into  that  file  in
              exactly  the  way  rsyslog  sees  them.  This option is useful for troubleshooting,
              especially if problems with the order of action processing  is  suspected.  It  may
              also be used to check for "unexepectedly" included config content.

       -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

       -v     Print version and exit.


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

              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 children 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 machine.

   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 information.
              The Unix domain socket to from where local syslog messages are read.
              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 FileTrace=expr.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
                     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 all.
              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
              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), savelog(8)


       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