SYSLOGD(8)

NAME
syslogd - log systems messages

SYNOPSIS
syslogd [-dsuv] [-a allowed_peer] [-f config_file] [-m mark_interval] [-p log_socket] [-l path]

DESCRIPTION
The syslogd daemon reads and logs messages to the system console, log files, other machines and/or users as specified by its configuration file. The options are as follows:

-a allowed_peer
    Allow allowed_peer to log to this syslogd using UDP datagrams. Multiple -a options may be specified.

    Allowed_peer can be any of the following:

    ipaddr/masklen[:service]
        Accept datagrams from ipaddr (in the usual dotted quad notation) with masklen bits being taken into account when doing the address comparision. If specified, service is the name or number of an UDP service (see services(5)) the source packet must belong to. A service of ‘*’ allows packets being sent from any UDP port. The default service is ‘syslog’. A missing masklen will be substituted by the historic class A or class B netmasks if ipaddr belongs into the address range of class A or B, respectively, or by 24 otherwise.

    domainname[:service]
        Accept datagrams where the reverse address lookup yields domainname for the sender address. The meaning of service is as explained above.

    *domainname[:service]
        Same as before, except that any source host whose name ends in domainname will get permission.

-d  Put syslogd into debugging mode. This is probably only of use to developers working on syslogd.

-f  Specify the pathname of an alternate configuration file; the default is /etc/syslog.conf.

-m  Select the number of minutes between “mark” messages; the default is 20 minutes.

-p  Specify the pathname of an alternate log socket to be used instead; the default is /var/run/log.

-l  Specify a location where syslogd should place an additional log socket. Up to 19 additional logging sockets can be specified. The primary use for this is to place additional log sockets in /dev/log of various chroot filespaces.

-s  Operate in secure mode. Do not log messages from remote machines. The messages will be received and counted and a log entry produced every time the count exceeds a power of two.

-u  Unique priority logging. Only log messages at the specified priority. Without this option, messages at the stated priority or higher are logged. This option changes the default comparison from “=>” to “=”.

-v  Verbose logging. If specified once, the numeric facility and priority are logged with each locally-written message. If specified more than once, the names of the facility and priority are logged with each locally-written message.

The syslogd daemon reads its configuration file when it starts up and whenever it receives a hangup signal. For information on the format of the configuration file, see syslog.conf(5).

The syslogd daemon reads messages from the UNIX domain socket /var/run/log, from an Internet domain socket specified in /etc/services, and from the special device /dev/klog (to read kernel messages).

The syslogd daemon creates the file /var/run/syslog.pid, and stores its process id there. This can be used to kill or reconfigure syslogd.

The message sent to syslogd should consist of a single line. The message can contain a priority code, which should be a preceding decimal number in angle braces, for example, ‘<5.>’ This priority code should map into the priorities defined in the include file <sys/syslog.h>.

FILES
/etc/syslog.conf
    configuration file
/var/run/syslog.pid
    process id of current syslogd
/var/run/log
    name of the UNIX domain datagram log socket
/dev/klog
    kernel log device

SEE ALSO
logger(1), syslog(3), services(5), syslog.conf(5)

HISTORY
The syslogd command appeared in 4.3BSD.

The -a, -s, -u, and -v options are FreeBSD 2.2 extensions.

BUGS
The ability to log messages received in UDP packets is equivalent to an unauthenticated remote disk-filling service, and should probably be disabled by default. Some sort of inter-syslogd authentication mechanism ought to be worked out. To prevent the worst abuse, use of the -a option is therefore highly recommended.

The -a matching algorithm doesn't pretend to be very efficient; use of numeric IP addresses is faster than domain name comparision. Since the allowed peer list is being walked linearly, peer groups where frequent messages are being anticipated from should be put early into the -a list.

The log socket was moved from /dev to ease the use of a read-only root filesystem. This may confuse some old binaries so that a symbolic link might be used for a transitional period.