Provided by: rsyslog_1.19.12-1_i386 bug


       rsyslogd - reliable and extended syslogd


       rsyslogd [ -4 ] [ -6 ] [ -A ] [ -a socket ] [ -d ] [ -e ]
       [ -f config file ] [ -h ] [ -i pid file ] [ -l hostlist ]
       [ -m interval ] [ -n ] [ -o ] [ -p socket ]
       [ -r [port] ] [ -s domainlist ] [ -t port,max-nbr-of-sessions ]
       [ -v ] [ -w ] [ -x ]


       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 (via UDP and TCP).

       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  MySQL 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
       insure 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 orginal 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.

       For details and configuration examples, see the  rsyslog.conf  (5)  man


       -A     When sending UDP messages, there are potentially multiple pathes
              to the target destination. By default, rsyslogd  only  sends  to
              the  first  target  it can successfully send to. If -A is given,
              messages are sent to all targets. This may improve  reliability,
              but  may  also  cause  message  duplicaton.  This  option should
              enabled only if it is fully understood.

       -4     Causes rsyslogd to listen to IPv4 addresses only.  If neither -4
              nor -6 is given, rsyslogd listens to all configured addresses of
              the system.

       -6     Causes rsyslogd to listen to IPv6 addresses only.  If neither -4
              nor -6 is given, rsyslogd listens to all configured addresses of
              the system.

       -a socket
              Using this argument you can specify additional sockets from that
              rsyslogd  has  to  listen to.  This is needed if you’re going to
              let some daemon run within a chroot() environment.  You can  use
              up  to  19  additional  sockets.  If your environment needs even
              more, you have  to  increase  the  symbol  MAXFUNIX  within  the
              syslogd.c  source  file.   An  example  for a chroot() daemon is
              described     by     the     people     from     OpenBSD      at

       -d     Turns  on  debug mode.  Using this the daemon will not proceed a
              fork(2) to set itself in the background, but  opposite  to  that
              stay  in  the foreground and write much debug information on the
              current tty.  See the DEBUGGING section for more information.

       -e     Set the default of $RepeatedMsgReduction config option to "off".
              Hine:  "e"  like  "every  message". For further information, see

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

       -h     By  default  rsyslogd will not forward messages it receives from
              remote hosts.  Specifying this switch on the command  line  will
              cause  the log daemon to forward any remote messages it receives
              to forwarding hosts which have been defined.

       -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.

       -l hostlist
              Specify a hostname that should be logged only  with  its  simple
              hostname  and  not  the  fqdn.   Multiple hosts may be specified
              using the colon (‘‘:’’) separator.

       -m interval
              The rsyslogd logs  a  mark  timestamp  regularly.   The  default
              interval  between  two -- MARK -- lines is 20 minutes.  This can
              be changed with this option.  Setting the interval to zero turns
              it off entirely.

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

       -o     Omit reading the standard local log socket. This option is  most
              useful  for  running  multiple instances of rsyslogd on a single
              machine. When specified, no local log socket is opened at all.

       -p socket
              You can specify an alternative unix  domain  socket  instead  of

       -r ["port"]
              Activates  the  syslog/udp  listener  service. The listener will
              listen to the specified port.  If no port  is  specified,  0  is
              used  as port number, which in turn will lead to a lookup of the
              system default syslog port. If there is no system  default,  514
              is  used.  Please note that the port must immediately follow the
              -r option. Thus "-r514" is valid while "-r 514" is invalid (note
              the space).

       -s domainlist
              Specify a domainname that should be stripped off before logging.
              Multiple domains  may  be  specified  using  the  colon  (‘‘:’’)
              separator.   Please  be  advised  that  no  sub-domains  may  be
              specified but only entire domains.  For example if  -s
              is    specified    and    the    host    logging   resolves   to
     no domain would be cut, you will have  to
              specify two domains like: -s

       -t port,max-nbr-of-sessions
              Activates  the  syslog/tcp  listener  service. The listener will
              listen  to  the  specified  port.  If   max-nbr-of-sessions   is
              specified,  that  becomes  the  maximum number of concurrent tcp
              sessions. If not specified, the default is 200. Please note that
              syslog/tcp  is  not  standardized,  but  the  implementation  in
              rsyslogd follows common practice and  is  compatible  with  e.g.
              Cisco  PIX,  syslog-ng  and  MonitorWare (Windows).  Please note
              that the port  must  immediately  follow  the  -t  option.  Thus
              "-t514" is valid while "-t 514" is invalid (note the space).

       -v     Print version and exit.

       -w     Supress  warnings  issued  when  messages are received from non-
              authorized machines (those, that are in no AllowedSender  list).

       -x     Disable DNS for remote messages.


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

              kill -SIGNAL ‘cat /var/run/‘

       SIGHUP This lets rsyslogd perform a re-initialization.  All open  files
              are    closed,    the    configuration    file    (default    is
              /etc/rsyslog.conf) will be reread and the rsyslog(3) facility is
              started again.

              Rsyslogd will die.

              If  debugging  is  enabled these are ignored, otherwise rsyslogd
              will die.

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

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


       Rsyslogd provides network support to  the  syslogd  facility.   Network
       support  means  that  messages  can  be forwarded from one node running
       rsyslogd to another node  running  rsyslogd  (or  a  compatible  syslog
       implementation) where they will be actually logged to a disk file.

       To  enable  this  you have to specify either the -r or -t option on the
       command line.  The default behavior is that rsyslogd  won’t  listen  to
       the  network.  You  can  also  combine  these  two  options if you want
       rsyslogd to listen to both TCP and UDP messages.

       The strategy is to have rsyslogd listen on a  unix  domain  socket  for
       locally  generated  log messages.  This behavior will allow rsyslogd to
       inter-operate with the syslog found in the standard C library.  At  the
       same  time  rsyslogd  listens  on the standard syslog port for messages
       forwarded  from  other  hosts.   To  have  this  work   correctly   the
       services(5)  files  (typically  found  in /etc) must have the following

                   syslog          514/udp

       If this entry is missing rsyslogd will use the well known port  of  514
       (so in most cases, it’s not really needed).

       To  cause  messages  to be forwarded to another host replace the normal
       file line in the rsyslog.conf file with the name of the host  to  which
       the  messages  is  to be sent prepended with an @ (for UDP delivery) or
       the sequence @@ (for TCP delivery). The host name can also be  followed
       by  a colon and a port number, in which case the message is sent to the
       specified port on the remote host.

              For example, to forward ALL messages to a remote  host  use  the
              following rsyslog.conf entry:

                   # Sample rsyslogd configuration file to
                   # messages to a remote host forward all.
                   *.*            @hostname
              More samples can be found in sample.conf.

              If  the  remote  hostname cannot be resolved at startup, because
              the name-server might not be accessible (it may be started after
              rsyslogd)  you  don’t  have  to  worry.   Rsyslogd will retry to
              resolve  the  name  ten  times  and  then   complain.    Another
              possibility   to   avoid  this  is  to  place  the  hostname  in

              With normal syslogds you would get syslog-loops if you send  out
              messages  that were received from a remote host to the same host
              (or more complicated to a third host that sends it back  to  the
              first one, and so on).

              To  avoid this no messages that were received from a remote host
              are sent out to another (or  the  same)  remote  host.  You  can
              disable this feature by the -h option.

              If  the  remote  host is located in the same domain as the host,
              rsyslogd is running on, only the simple hostname will be  logged
              instead of the whole fqdn.

              In  a local network you may provide a central log server to have
              all the important information  kept  on  one  machine.   If  the
              network consists of different domains you don’t have to complain
              about logging fully qualified names instead of simple hostnames.
              You  may want to use the strip-domain feature -s of this server.
              You can tell rsyslogd to strip off several  domains  other  than
              the  one the server is located in and only log simple hostnames.

              Using the -l option there’s also a possibility to define  single
              hosts  as  local  machines.   This, too, results in logging only
              their simple hostnames and not the fqdns.


       Rsyslogd has support for writing data to  MySQL  database  tables.  The
       exact specifics are described in the rsyslog.conf (5) man page. Be sure
       to read it if you plan to use database logging.

       While it is often handy to have the data in a  database,  you  must  be
       aware of the implications. Most importantly, database logging takes far
       longer than logging to a text file. A system that can  handle  a  large
       log  volume  when  writing  to  text files can most likely not handle a
       similar large volume when writing to a database table.


       Rsyslogd has support for logging output to named pipes (fifos).  A fifo
       or  named  pipe  can  be  used  as  a  destination  for log messages by
       prepending a pipy symbol (‘‘|’’) to the name  of  the  file.   This  is
       handy  for  debugging.   Note  that  the  fifo must be created with the
       mkfifo command before rsyslogd is started.

              The following configuration file routes debug messages from  the
              kernel to a fifo:

                   # Sample configuration to route kernel debugging
                   # messages ONLY to /usr/adm/debug which is a
                   # named pipe.
                   kern.=debug              |/usr/adm/debug


       There is probably one important consideration when installing rsyslogd.
       It is  dependent  on  proper  formatting  of  messages  by  the  syslog
       function.   The  functioning  of  the  syslog  function  in  the shared
       libraries changed somewhere in the region  of[2-4].n.   The
       specific  change  was to null-terminate the message before transmitting
       it to the /dev/log socket.   Proper  functioning  of  this  version  of
       rsyslogd is dependent on null-termination of the message.

       This  problem  will  typically manifest itself if old statically linked
       binaries are being used on the system.  Binaries using old versions  of
       the syslog function will cause empty lines to be logged followed by the
       message with the first character in  the  message  removed.   Relinking
       these  binaries  to newer versions of the shared libraries will correct
       this problem.

       The rsyslogd(8) can be run from init(8) or started as part of the  rc.*
       sequence.   If  it  is  started  from  init  the option -n must be set,
       otherwise you’ll get tons of syslog daemons started.  This  is  because
       init(8) depends on the process ID.


       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 since rsyslogd will be unable to  bind  to  the  514/UDP

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

       5.     Use step 4 and if the problem persists and is not secondary to a
              rogue  program/daemon  get  a 3.5 ft (approx. 1 meter) length of
              sucker rod* and have a chat with the user in question.

              Sucker rod def. — 3/4, 7/8 or  1in.  hardened  steel  rod,  male
              threaded  on  each  end.   Primary  use  in  the oil industry in
              Western North Dakota and other locations to pump ’suck’ oil from
              oil  wells.   Secondary  uses are for the construction of cattle
              feed lots and for dealing with the  occasional  recalcitrant  or
              belligerent individual.

   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 reply  recorded  messages  or  spoof  a
       sender’s  IP  address, which could lead to a wrong preception of system
       activity. Be  sure  to  think  about  syslog  network  security  before
       enabling it.


       When  debugging is turned on using -d option then rsyslogd will be very
       verbose by writing much of  what  it  does  on  stdout.   Whenever  the
       configuration  file  is  reread  and  re-parsed  you’ll  see a tabular,
       corresponding to the internal data structure.  This tabular consists of
       four fields:

       number This  field  contains  a  serial  number starting by zero.  This
              number represents the position in the  internal  data  structure
              (i.e. the array).  If one number is left out then there might be
              an error in the corresponding line in /etc/rsyslog.conf.

              This field is  tricky  and  represents  the  internal  structure
              exactly.    Every   column  stands  for  a  facility  (refer  to
              syslog(3)).  As you can see, there  are  still  some  facilities
              left  free  for  former use, only the left most are used.  Every
              field  in  a  column  represents  the   priorities   (refer   to

       action This  field  describes  the  particular  action that takes place
              whenever a message is received that matches the pattern.   Refer
              to the syslog.conf(5) manpage for all possible actions.

              This field shows additional arguments to the actions in the last
              field.  For file-logging this is the filename for  the  logfile;
              for  user-logging  this  is  a list of users; for remote logging
              this is the hostname of the machine  to  log  to;  for  console-
              logging  this  is  the used console; for tty-logging this is the
              specified tty; wall has no additional arguments.

              There will also be a second internal structure which  lists  all
              defined  templates  and there contents. This also enables you to
              see the internally-defined, hardcoded templates.


              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.


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

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

       Michael Meckelein
       Adiscon GmbH