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IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)syslog.conf.5 8.1 (Berkeley) 6/9/93 .\" $FreeBSD$ .\" .Dd February 21, 2021 .Dt SYSLOG.CONF 5 .Os sysklogd .Sh NAME .Nm syslog.conf .Nd configuration file format for .Xr syslogd 8 .Sh DESCRIPTION The .Nm file is the configuration file for the .Xr syslogd 8 program. It consists of lines of rules for logging, with each line containing at least two fields: the .Em selector field which specifies the types of messages and priorities to which the line applies, and an .Em action field which specifies the action to be taken if a message .Xr syslogd 8 receives matches the selection criteria. A rule may also have an .Em option field for a setting that applies only to that rule. .Pp The fields are separated by one or more tab characters or spaces. A rule may be divided into several lines if the leading line ends with a single backslash ('\\') character. .Pp .Bd -literal -offset indent RULE := SELECTOR ACTION [;OPTION] SELECTOR := [SELECTOR;]facility[,facility].[!=]severity ACTION := /path/to/file |= |/path/to/named/pipe |= @remote[.host.tld][:PORT] OPTION := [OPTION,] |= RFC3164 |= RFC5424 |= rotate=SIZE:COUNT secure_mode [0,1,2] include /etc/syslog.d/*.conf notify /path/to/script-on-rotate .Ed .Pp The .Em selector field specifies a pattern of facilities and priorities belonging to the specified action. The .Em action details where or what to do with the selected input. The .Em option field, which must start with the semi-colon option delimiter (';'), currently supports log formatting and log rotation. The default log format is the traditional RFC3164 (included here for completeness), .Sy except for remote syslog targets where the BSD format (without both timestamp and hostname) is the default. The user must explicitly set RFC3164 on a remote logging target. RFC5424 is the newest format with RFC3339 time stamps, msgid, structured data, and more. The BSD format cannot be set, it is only the default for remote targets for compatibility reasons. .Pp .Bl -tag -compact -width "RFC3164:" .It Sy BSD: .Li myproc[8710]: Kilroy was here. .It Sy RFC3164: .Li Aug 24 05:14:15 192.0.2.1 myproc[8710]: Kilroy was here. .It Sy RFC5424: .Li 2003-08-24T05:14:15.000003-07:00 192.0.2.1 myproc 8710 - - Kilroy was here. .El .Pp The log rotation, which is only relevant for files, details the max .Ar SIZE:COUNT a file can reach before it is rotated, and later compressed. This feature is mostly intended for embedded systems that do not want to have cron or a separate log rotate daemon. .Pp .Sy Note: the permissions of the rotated files are kept. Meaning the administrator can create all log files, before starting .Nm the first time, with the permissions needed for the site. However, if the log files do not exist, .Nm will create them with the user and group it runs as and 0644 permissions. .Pp Comments, lines starting with a hash mark ('#'), and empty lines are ignored. If an error occurs during parsing the whole line is ignored. .Pp Additional options include .Ql secure_mode <0-2> which is the same as the .Nm syslogd Fl s commandline option. .Sy Note: command line option always wins, so you need to drop .Fl s from the command line to use this .conf file option instead. .Pp .Bl -tag -compact -width "01" -offset indent .It 0 act as a syslog sink, listening on UDP port 514 by default, as well as support for sending to remote syslog servers .It 1 only support for sending to remote syslog servers, no Internet ports open .It 2 no Internet ports open at all, and no remote logging possible .El .Bd -literal -offset indent # Example: only allow logging to remote servers secure_mode 1 .Ed .Pp The .Ql notify option specifies the path to an executable program which will get called whenever a log file has been rotated, with the name of the file, less its rotation suffix .Ql .0 , as an argument. For example: .Ql notify /sbin/on-log-rotate.sh . Any number of notifiers may be installed. .Pp The .Ql include option can be used to include all files with names ending in '.conf' and not beginning with a '.' contained in the directory following the keyword. This keyword can only be used in the first level configuration file. The included example .Pa /etc/syslog.conf has the following at the end: .Bd -literal -offset indent # # Drop your subsystem .conf file in /etc/syslog.d/ # include /etc/syslog.d/*.conf .Ed .Pp Note that if you use spaces as separators, your .Nm might be incompatible with other Unices or Unix-like systems. This functionality was added for ease of configuration (e.g.\& it is possible to cut-and-paste into .Nm ) , and to avoid possible mistakes. This change however preserves backwards compatibility with the old style of .Nm (i.e., tab characters only). .Sh SELECTORS The selector field consists of two parts, a .Em facility and a .Em priority , separated by a period ('.'). Both parts are case insensitive and can also be specified as decimal numbers corresponding to the definitions in .Pa /usr/include/syslog.h . It is safer to use symbolic names rather than decimal numbers. Both facilities and priorities are described in .Xr syslogp 3 . The names mentioned below correspond to the similar .Ql LOG_FOO values in .Pa /usr/include/syslog.h . .Pp The .Em facility is one of the following keywords: .Bl -column "Code" "Facility" "Description" -offset indent .It Sy "Code" Ta Sy "Facility" Ta Sy "Description" .It 0 Ta kern Ta Kernel log messages .It 1 Ta user Ta User-level messages .It 2 Ta mail Ta Mail system .It 3 Ta daemon Ta General system daemons .It 4 Ta auth Ta Security/authorization messages .It 5 Ta syslog Ta Messages generated by syslogd .It 6 Ta lpr Ta Line printer subsystem .It 7 Ta news Ta Network news subsystem .It 8 Ta uucp Ta UNIX-to-UNIX copy .It 9 Ta cron Ta Clock/cron daemon (BSD, Linux) .It 10 Ta authpriv Ta Security/authorization messages (private) .It 11 Ta ftp Ta FTP daemon .It 12 Ta ntp Ta NTP subsystem .It 13 Ta security Ta Log audit .It 14 Ta console Ta Log alert .It 15 Ta unused Ta Clock/cron daemon (Solaris) .It 16 Ta local0 Ta Reserved for local/system use .It 17 Ta local1 Ta Reserved for local/system use .It 18 Ta local2 Ta Reserved for local/system use .It 19 Ta local3 Ta Reserved for local/system use .It 20 Ta local4 Ta Reserved for local/system use .It 21 Ta local5 Ta Reserved for local/system use .It 22 Ta local6 Ta Reserved for local/system use .It 23 Ta local7 Ta Reserved for local/system use .El .Pp Notice, several of the above listed facilities are not supported by the standard C library (GLIBC, musl libc, or uClibc) on Linux. libsyslog, shipped with .Nm sysklogd , however, supports all the above facilities in full. Also, the keyword .Ql mark is only for internal use and should therefore not be used in applications. The .Em facility specifies the subsystem that produced the message, e.g. all mail programs log with the mail facility, .Ql LOG_MAIL , if they log using syslog. .Pp In most cases anyone can log to any facility, so we rely on convention for the correct facility to be chosen. However, generally only the kernel can log to the .Ql kern facility. This because the implementation of .Xr openlog 3 and .Xr syslog 3 in GLIBC does not allow logging to the .Ql kern facility. .Pp The .Em priority is one of the following keywords, in ascending order: .Bl -column "Code" "Facility" "Description" -offset indent .It Sy "Value" Ta Sy "Severity" Ta Sy "Description" .It 0 Ta emergency Ta System is unusable .It 1 Ta alert Ta Action must be taken immediately .It 2 Ta critical Ta Critical conditions .It 3 Ta error Ta Error conditions .It 4 Ta warning Ta Warning conditions .It 5 Ta notice Ta Normal but significant conditions .It 6 Ta info Ta Informational messages .It 7 Ta debug Ta Debug-level messages .El .Pp The default log level of most applications is .Ql notice , meaning only .Ql notice and above are forwarded to .Nm syslogd . See .Xr setlogmask 3 for more information on how to change the default log level of your application. .Pp In addition to the above mentioned facility and priority names, .Xr syslogd 8 understands the following extensions: .Pp .Bl -tag -compact -width "'none'" .It * An asterisk ('*') matches all facilities or all priorities, depending on where it is used (before or after the period). .It none The keyword .Ql none stands for no priority of the given facility. .It , Multiple facilities may be specified for a single priority pattern in one statement using the comma (',') operator to separate the facilities. You may specify as many facilities as you want. Please note that only the facility part from such a statement is taken, a priority part would be ignored. .It ; Multiple selectors may be specified for a single .Em action using the semicolon (';') separator. Selectors are processed from left to right, with each selector being able to overwrite preceding ones. Using this behavior you are able to exclude some priorities from the pattern. .It = This version of .Xr syslogd 8 has a syntax extension to the original BSD source, which makes its use more intuitive. You may precede every priority with an equation sign ('=') to specify that only this single priority should be matched, instead of the default: this priority and all higher priorities. .It ! You may also precede the priority with an exclamation mark ('!') if you want to ignore this priority and all higher priorities. You may even use both the exclamation mark and the equation sign if you want to ignore a single priority. If both extensions are used, the exclamation mark must occur before the equation sign. .El .Sh ACTIONS The action field of a rule is the destination or target for a match. It can be a file, a UNIX named pipe, the console, or a remote machine. .Ss Regular File Typically messages are logged to real files. The filename is specified with an absolute path name. .Pp You may prefix each entry with a minus sign ('-') to avoid syncing the file after each log message. Note that you might lose information if the system crashes right after a write attempt. Nevertheless this might give you back some performance, especially if you run programs that use logging in a very verbose manner. .Ss Named Pipes This version of .Xr syslogd 8 supports logging to named pipes (FIFOs). A FIFO, or named pipe, can be used as a destination for log messages by prepending a pipe symbol ('|') to the name of the file. This can be very handy for debugging. Note that the FIFO must be created with the .Xr mkfifo 1 command before .Nm syslogd is started. .Ss Terminal and Console If the file you specified is a tty, special tty-handling is done, same with .Pa /dev/console . .Ss Remote Machine Full remote logging support is available in .Nm syslogd , i.e. to send messages to a remote syslog server, and and to receive messages from remote hosts. To forward messages to another host, prepend the hostname with the at sign ('@'). If a port number is added after a colon (':') then that port will be used as the destination port rather than the usual syslog port. .Pp This feature makes it possible to collect all syslog messages in a network on a central host. This reduces administration needs and can be really helpful when debugging distributed systems. .Pp Using a named pipe log method, messages from remote hosts can be sent to a log program. By reading log messages line by line such a program is able to sort log messages by host name or program name on the central log host. This way it is possible to split the log into separate files. .Pp By default messages to remote remote hosts were formatted in the original BSD style, without timestamp or hostname. As of .Nm syslogd v2.0 the default includes timestamp and hostname. It is also possible to enable the new RFC5424 style formatting, append ';RFC5424' after the hostname. .Ss List of Users Usually critical messages are also directed to .Ql root on that machine. You can specify a list of users that ought to receive the log message on their terminal by writing their usernames. You may specify more than one user by separating the usernames with commas (','). Only logged in users will receive the log messages. .Ss Everyone logged on Emergency messages often go to all users currently online to notify them that something strange is happening with the system. To specify this .Xr wall 1 feature use an asterisk ('*'). .Sh IMPLEMENTATION NOTES The .Dq kern facility is usually reserved for messages generated by the local kernel. Other messages logged with facility .Dq kern are usually translated to facility .Dq user . This translation can be disabled; see .Xr syslogd 8 for details. .Sh FILES .Bl -tag -width /etc/syslog.d/*.conf -compact .It Pa /etc/syslog.conf .Xr syslogd 8 configuration file .It /etc/syslog.d/*.conf Recommended directory for .conf snippets .El .Sh EXAMPLES This section lists some examples, partially from actual site setups. .Ss Catch Everything This example matches all facilities and priorities and stores everything in the file .Pa /var/log/syslog in RFC5424 format. Every time the file reaches 10 MiB it is rotated and five files in total are kept, including the non-rotated file. .Bd -literal -offset indent # Match all log messages, store in RC5424 format and rotate every 10 MiB # *.* /var/log/critical ;rotate=10M:5,RFC5424 .Ed .Ss Critical This stores all messages of priority .Ql crit in the file .Pa /var/log/critical , with the exception of any kernel messages. .Bd -literal -offset indent # Store critical stuff in critical # *.=crit;kern.none /var/log/critical .Ed .Ss Kernel This is an example of the 2nd selector overwriting part of the first one. The first selector selects kernel messages of priority .Ql info and higher. The second selector filters out kernel messages of priority .Ql error and higher. This leaves just priorities .Ql info , .Ql notice , and .Ql warning to get logged. .Bd -literal -offset indent # Kernel messages are stored in the kernel file, critical messages and # higher ones also go to another host and to the console # kern.* /var/log/kernel kern.crit @arpa.berkeley.edu ;RFC5424 kern.crit /dev/console kern.info;kern.!err /var/log/kernel.info .Ed .Pp The first rule directs any message that has the kernel facility to the file .Pa /var/log/kernel . Recall that only the kernel itself can log to this facility. .Pp The second statement directs all kernel messages of priority .Ql crit and higher to the remote host .Ql arpa.berkeley.edu in RFC5424 style formatting. This is useful, because if the host crashes and the disks get irreparable errors you might not be able to read the stored messages. If they're on a remote host, too, you still can try to find out the reason for the crash. .Pp The third rule directs kernel messages of priority .Ql crit and higher to the actual console, so the person who works on the machine will get them, too. .Pp The fourth line tells .Nm syslogd to save all kernel messages that come with priorities from .Ql info up to .Ql warning in the file .Pa /var/log/kernel.info . .Ss Redirecting to a TTY This directs all messages that use .Ql mail.info (in source .Ql LOG_MAIL | LOG_INFO ) to .Pa /dev/tty12 , the 12th console. For example the tcpwrapper .Xr tcpd 8 uses this as its default. .Bd -literal -offset indent # The tcp wrapper logs with mail.info, we display # all the connections on tty12 # mail.=info /dev/tty12 .Ed .Ss Redirecting to a file This pattern matches all messages that come with the .Ql mail facility, except for the .Ql info priority. These will be stored in the file .Pa /var/log/mail . .Bd -literal -offset indent # Write all mail related logs to a file # mail.*;mail.!=info /var/log/mail .Ed .Ss Single Priority from Two Facilities This will extract all messages that come either with .Ql mail.info or with .Ql news.info and store them in the file .Pa /var/log/info . .Bd -literal -offset indent # Log all mail.info and news.info messages to info # mail,news.=info /var/log/info .Ed .Ss Advanced Filtering, part 1 This logs all messages that come with either the .Ql info or the .Ql notice priority into the file .Pa /var/log/messages , except for all messages that use the .Ql mail facility. .Bd -literal -offset indent # Log info and notice messages to messages file # *.=info;*.=notice;\\ mail.none /var/log/messages .Ed .Ss Advanced Filtering, part 2 This statement logs all messages that come with the .Ql info priority to the file .Pa /var/log/messages . But any message with either .Ql mail or the .Ql news facility are not logged. .Bd -literal -offset indent # Log info messages to messages file # *.=info;\\ mail,news.none /var/log/messages .Ed .Ss Wall Messages This rule tells .Nm syslogd to write all emergency messages to all currently logged in users. This is the wall action. .Bd -literal -offset indent # Emergency messages will be displayed using wall # *.=emerg * .Ed .Ss Alerting Users This rule directs all messages of priority .Ql alert or higher to the terminals of the operator, i.e. of the users 'root' and 'eric', if they're logged in. .Bd -literal -offset indent # Any logged in root user and Eric get alert and higher messages. # *.alert root,eric .Ed .Ss Log Rotation This example logs all messages except kernel messages to the file .Pa /var/log/messages without syncing ('-') the file after each log message. When the file reaches 100 kiB it is rotated. In total are only 10 rotated files, including the main file itself and compressed files kept. The size argument takes the same modifiers as the .Xr syslogd 8 command line option, .Fl r . .Bd -literal -offset indent # Log all messages, including kernel, to the messages file rotate it # every 100 kiB and keep up to 10 aged out, and compressed, files. # *.*;kern.none -/var/log/messages ;rotate=100k:10 .Ed .Ss Logging to Remote Syslog Server This rule redirects all messages to one remote host called .Ql finlandia , with RFC5424 style formatting, and another remote host called .Ql sibelius , but on a non-standard port and with RFC3164 formatting (i.e., including timestamp and hostname). .Bd -literal -offset indent *.* @finlandia ;RFC5424 *.* @sibelius:5514 ;RFC3164 .Ed .Sh SEE ALSO .Xr syslog 3 , .Xr syslogd 8 .Sh BUGS The effects of multiple .Em selectors are sometimes not intuitive. For example .Dq mail.crit,*.err will select .Dq mail facility messages at the level of .Dq err or higher, not at the level of .Dq crit or higher. .Pp In networked environments, note that not all operating systems implement the same set of facilities. The facilities authpriv, cron, ftp, and ntp that are known to this implementation might be absent on the target system. Even worse, DEC UNIX uses facility number 10 (which is authpriv in this implementation) to log events for their AdvFS file system.