Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

SYSLOG.CONF(5)                File Formats Manual               SYSLOG.CONF(5)

     syslog.conf - syslogd(8) configuration file

     The syslog.conf file is the configuration file for the syslogd(8)
     program.  It consists of extended options (lines with one key="value"
     assignment) and blocks of lines separated by program and hostname
     specifications, with each line containing two fields: the selector field
     which specifies the types of messages and priorities to which the line
     applies, and an action field which specifies the action to be taken if a
     message syslogd(8) receives matches the selection criteria.  The selector
     field is separated from the action field by one or more tab characters.

     The Selectors function are encoded as a facility, a period (`.'), an
     optional set of comparison flags ([!] [<=>]), and a level, with no
     intervening white-space.  Both the facility and the level are case

     The facility describes the part of the system generating the message, and
     is one of the following keywords: auth, authpriv, cron, ftp, daemon,
     kern, lpr, mail, mark, news, syslog, user, uucp and local0 through
     local7.  These keywords (with the exception of mark) correspond to the
     similar "LOG_" values specified to the openlog(3) and syslog(3) library

     The comparison flags may be used to specify exactly what levels are
     logged.  If unspecified, the default comparison is `>=' (greater than or
     equal to), or, if the -U option is passed to syslogd(8), `=' (equal to).
     Comparison flags beginning with `!' will have their logical sense
     inverted.  Thus, `!=info' means all levels except info and `!notice' has
     the same meaning as `<notice'.

     The level describes the severity of the message, and is a keyword from
     the following ordered list (higher to lower): emerg, alert, crit, err,
     warning, notice, info and debug.  These keywords correspond to the
     similar (LOG_) values specified to the syslog(3) library routine.

     Each block of lines is separated from the previous block by a program or
     hostname specification.  A block will only log messages corresponding to
     the most recent program and hostname specifications given.  Consider the
     case of a block that selects `pppd' as the program, directly followed by
     a block that selects messages from the hostname `dialhost'.  The second
     block will log only messages from the pppd(8) program from the host

     A program specification of the form `#!+prog1,prog2' or `!+prog1,prog2'
     will cause subsequent blocks to be applied to messages logged by the
     specified programs.  A program specification of the form `#!-prog1,prog2'
     or `!-prog1,prog2' will cause subsequent blocks to be applied to messages
     logged by programs other than the ones specified.  A program
     specification of the form `#!prog1,prog2' or `!prog1,prog2' is equivalent
     to `!+prog1,prog2'.  Program selectors may also match kernel-generated
     messages.  For example, a program specification of `!+subsys' will match
     kernel-generated messages of the form `subsys: here is a message'.  The
     special specification `!*' will cause subsequent blocks to apply to all

     A hostname specification of the form `#+host1,host2' or `+host1,host2'
     will cause subsequent blocks to be applied to messages received from the
     specified hosts.  A hostname specification of the form `#-host1,host2' or
     `-host1,host2' will cause subsequent blocks to be applied to messages
     from hosts other than the ones specified.  If the hostname is given as
     `@', the local hostname will be used.  The special specification `+*'
     will cause subsequent blocks to apply to all hosts.

     See syslog(3) for a further descriptions of both the facility and level
     keywords and their significance.  It is preferred that selections be made
     based on facility rather than program, since the latter can vary in a
     networked environment.  However, there are cases where a facility may be
     too broadly defined.

     If a received message matches the specified facility, and the specified
     level comparison is true, and the first word in the message after the
     date matches the program, the action specified in the action field will
     be taken.

     Multiple selectors may be specified for a single action by separating
     them with semicolon (`;') characters.  It is important to note, however,
     that each selector can modify the ones preceding it.

     Multiple facilities may be specified for a single level by separating
     them with comma (`,') characters.

     An asterisk (`*') can be used to specify all facilities or all levels.

     The special facility "mark" receives a message at priority "info" every
     20 minutes (see syslogd(8)).  This is not enabled by a facility field
     containing an asterisk.

     The special level "none" disables a particular facility.

     The action field of each line specifies the action to be taken when the
     selector field selects a message.  There are five forms:

        A pathname (beginning with a leading slash).  Selected messages are
         appended to the file, unless pathname points to an existing FIFO
         special file.  syslogd(8) treats FIFO specially by opening them in
         non-blocking mode and discarding messages sent when no reader is
         listening on the other side.

         To ensure that kernel messages are written to disk promptly,
         syslogd(8) calls fsync(2) after writing messages from the kernel.
         Other messages are not synced explicitly.  You may disable syncing of
         files specified to receive kernel messages by prefixing the pathname
         with a minus sign `-'.  Note that use of this option may cause the
         loss of log information in the event of a system crash immediately
         following the write attempt.  However, using this option may prove to
         be useful if your system's kernel is logging many messages.

         Normally the priority and version is not written to file.  In order
         to use syslog-sign you may prefix a pathname with the plus sign `+'.
         If both switches are used the order has to be `+-'.

        A hostname (preceded by an at (`@') sign).  Selected messages are
         forwarded to the syslogd(8) program on the named host with UDP.

        A hostname preceded by an at (`@') sign and enclosed in brackets
         (`[]') Selected messages are forwarded with TLS to the syslogd(8)
         program on the named host.  After the closing bracket a colon (`:')
         and a port or service name may be appended.  Additional options are
         configured in parentheses in the form of key="value".  Recognized
         keywords are subject, fingerprint, cert, and verify.

        A comma separated list of users.  Selected messages are written to
         those users if they are logged in.

        An asterisk.  Selected messages are written to all logged-in users.

        A vertical bar (`|') followed by a command to which to pipe the
         selected messages.  The command string is passed to /bin/sh for
         evaluation, so the usual shell metacharacters or input/output
         redirection can occur.  (Note that redirecting stdio(3) buffered
         output from the invoked command can cause additional delays, or even
         lost output data in case a logging subprocess exits with a signal.)
         The command itself runs with stdout and stderr redirected to
         /dev/null.  Upon receipt of a SIGHUP, syslogd(8) will close the pipe
         to the process.  If the process does not exit voluntarily, it will be
         sent a SIGTERM signal after a grace period of up to 60 seconds.

         The command will only be started once data arrives that should be
         piped to it.  If the command exits, it will be restarted as

         If it is desired that the subprocess should receive exactly one line
         of input, this can be achieved by exiting after reading and
         processing the single line.  A wrapper script can be used to achieve
         this effect, if necessary.  Note that this method can be very
         resource-intensive if many log messages are being piped through the

         Unless the command is a full pipeline, it may be useful to start the
         command with exec so that the invoking shell process does not wait
         for the command to complete.  Note that the command is started with
         the UID of the syslogd(8) process, normally the superuser.

         Just like with files a plus sign `+' will leave the priority and
         version information intact.

     Blank lines and lines whose first non-blank character is a hash (`#')
     character are ignored.

     Additional options are used for TLS configuration:

     Enables TLS server mode.

     Service name or port number to bind to.  Default is `syslog'.  As long as
     no official port is assigned this option is required for TLS servers.

     Hostname or IP to bind to.

     Automatically generate a private key and certificate.

     File with private key.  Default is `/etc/openssl/default.key'

     File with certificate to use.  Default is `/etc/openssl/default.crt'

     File with CA certificate to use.

     Directory containing CA certificates.

     If set to `off' then certificate authentication is skipped.

     List of fingerprints of trusted client certificates.

     List of filenames with trusted client certificates.

     One function of TLS is mutual authentication of client and server.
     Unless authentication is disabled by setting `tls_verify=off' the
     following rules are used:

   As client:
     A client can be configured not to check a server's certificate by setting
     the parameter verify to `off'.  If the server's certificate is signed by
     a trusted CA then it is checked if its hostname or IP is given in its
     certificate (as a CommonName, as a DNS SubjectAltName, or as an IP
     SubjectAltName).  If any match is found then the server is authenticated.
     If a subject parameter is given then it is can satisfy this test as well.
     This allows DNS-independent configurations using the server's IP address
     in the destination and adding its hostname as subject to authenticate the
     TLS connection without having to add the IP to the X.509 certificate.

     If no CA is used or no trust path between CA and server certificate
     exists, then hash value of the server's certificate is compared with the
     hash given in fingerprint and the hash of the certificate in cert.  If
     the hashes are equal then the server is authenticated.

   As server:
     If using a CA and the client's certificate is signed by it then the
     client is authenticated.  Otherwise the hash of the client's certificate
     is compared with the hashes given in tls_allow_fingerprints and the
     hashes of the certificates given in tls_allow_clientcerts.  On any match
     the client is authenticated.

     syslogd(8) is able to buffer temporary not writable messages in memory.
     To limit the memory consumed for this buffering the following options may
     be given:



     The maximum number of messages buffered for one destination of type tls,
     file, or pipe respectively.  Defaults are `1024', `1024', and `-1' (no



     The maximum memory usage in bytes of messages buffered for one
     destination.  Defaults are `1M', `1M', and `16M'.

     syslogd(8) is able to digitally sign all processed messages.  The used
     protocol is defined by RFC 5848 (syslog-sign): at the start of a session
     the signing sender sends so called certificate blocks containing its
     public key; after that it periodically sends a signed message containing
     hashes of previous messages.

     To detect later manipulation one has to keep a copy of the key used for
     signing (otherwise an attacker could alter the logs and sign them with
     his own key).  If TLS is used with a DSA key then the same key will be
     used for signing.  This is the recommended setup because it makes it easy
     to have copies of the certificate (with the public key) in backups.
     Otherwise new keys are generated on every restart and for certain
     verification it is necessary to have copies of all used keys.  So logging
     only to a local file is not secure; at least the used keys should be
     logged to another host.

     Enables signing.  Set this option to enable syslog-sign and select how to
     assign messages to signature groups (subsets of messages that are signed
     together).  To enable later signature verification and detection of lost
     messages the assignment should be chosen such that all messages of one
     signature group are written to the same file.  Four possible values for
     this option are:

           0       Use one global signature group for all messages.

           1       Use one signature group per priority.

           2       Use signature groups for ranges of priorities.

           3       Use one signature group per destination.  This is a custom
                   strategy not defined by the standard.  With this setting
                   one signature group is set up for every file and network

     This option is only evaluated with `sign_sg=2' and allows to configure
     the priority ranges for signature groups.  The parameters are numerical
     values used as the maximum priority for one group.  The default is to use
     one signature groups per facility, which is equal to setting
     `sign_delim_sg2=7 15 23 31 39 ...'.

     /etc/syslog.conf  The syslogd(8) configuration file.
                       Example script to verify message signatures.  (Requires
                       Perl and modules not part of NetBSD.)

     A configuration file might appear as follows:

     # Log all kernel messages, authentication messages of
     # level notice or higher and anything of level err or
     # higher to the console.
     # Don't log private authentication messages!
     *.err;kern.*;auth.notice;authpriv.none  /dev/console

     # Log anything (except mail) of level info or higher.
     # Don't log private authentication messages!
     *.info;mail.none;authpriv.none          /var/log/messages

     # Log daemon messages at debug level only
     daemon.=debug                           /var/log/daemon.debug

     # The authpriv file has restricted access.
     # Write logs with priority for later verification with syslog-sign.
     authpriv.*                              +/var/log/secure

     # Log all the mail messages in one place.
     mail.*                                  /var/log/maillog

     # Everybody gets emergency messages, plus log them on another
     # machine.
     *.emerg                                 *
     *.emerg                                 @arpa.berkeley.edu

     # Log all messages of level info or higher to another
     # machine using TLS with an alternative portname and a
     # fingerprint for authentication
     *.info                  @[logserver]:1234(fingerprint="SHA1:01:02:...")

     # Root and Eric get alert and higher messages.
     *.alert                                 root,eric

     # Save mail and news errors of level err and higher in a
     # special file.
     mail,news.err                           /var/log/spoolerr

     # Pipe all authentication messages to a filter.
     auth.*                                  |exec /usr/local/sbin/authfilter

     # Log kernel messages to a separate file without syncing each message.
     kern.*                                  -/var/log/kernlog

     # Save ftpd transactions along with mail and news.
     *.*                                     /var/log/spoolerr

     # Send all error messages from a RAID array through a filter.
     kern.err                                |exec /usr/local/sbin/raidfilter

     # Save pppd messages from dialhost to a separate file.
     *.*                                     /var/log/dialhost-pppd

     # Save non-local log messages from all programs to a separate file.
     *.*                                     /var/log/foreign

     # Generate digital signatures for all messages
     # to each file or network destination.

     syslog(3), syslogd(8)

     The syslog.conf file appeared in 4.3BSD, along with syslogd(8).

     The effects of multiple selectors are sometimes not intuitive.  For
     example "mail.crit;*.err" will select "mail" facility messages at the
     level of "err" or higher, not at the level of "crit" or higher.

NetBSD 10.99                   November 9, 2013                   NetBSD 10.99