NAME
syslogd
—
log systems messages
SYNOPSIS
syslogd |
[-468ACcdkNnosTuv ] [-a
allowed_peer] [-b
bind_address] [-f
config_file] [-l
[mode:]path]
[-m mark_interval]
[-P pid_file]
[-p log_socket] |
DESCRIPTION
Thesyslogd
utility 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:
-4
- Force
syslogd
to use IPv4 addresses only. -6
- Force
syslogd
to use IPv6 addresses only. -8
- Tells
syslogd
not to interfere with 8-bit data. Normallysyslogd
will replace C1 control characters (ISO 8859 and Unicode characters) with their “M-x” equivalent. Note, this option does not change the waysyslogd
alters control characters (see iscntrl(3)). They will always be replaced with their “^x” equivalent. -A
- Ordinarily,
syslogd
tries to send the message to only one address even if the host has more than one A or AAAA record. If this option is specified,syslogd
tries to send the message to all addresses. -a
allowed_peer- Allow allowed_peer to log to this
syslogd
using UDP datagrams. Multiple-a
options may be specified.The allowed_peer option may 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 comparison.
ipaddr can be also IPv6 address by enclosing the
address with ‘
[
’ and ‘]
’. 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
’. If ipaddr is IPv4 address, 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. If ipaddr is IPv6 address, a missing masklen will be substituted by 128. - 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.
The
-a
options are ignored if the-s
option is also specified. -b
bind_address[:service]-b
: service- Bind to a specific address and/or port. The address can be specified as a
hostname, and the port as a service name. If an IPv6 address is specified,
it should be enclosed with ‘
[
’ and ‘]
’. The default service is ‘syslog
’. -C
- Create log files that do not exist (permission is set to
0600
). -c
- Disable the compression of repeated instances of the same line into a
single line of the form “
last message repeated N times
” when the output is a pipe to another program. If specified twice, disable this compression in all cases. -d
- Put
syslogd
into debugging mode. This is probably only of use to developers working onsyslogd
. -f
- Specify the pathname of an alternate configuration file; the default is /etc/syslog.conf.
-k
- Disable the translation of messages received with facility “kern” to facility “user”. Usually the “kern” facility is reserved for messages read directly from /dev/klog.
-m
- Select the number of minutes between “mark” messages; the default is 20 minutes.
-N
- Disable binding on UDP sockets. RFC 3164 recommends that outgoing syslogd
messages should originate from the privileged port, this option
disables
the recommended behavior. This option inherits
-s
. -n
- Disable dns query for every request.
-o
- Prefix kernel messages with the full kernel boot file as determined by
getbootfile(3). Without this, the kernel message prefix is
always “
kernel:
”. -p
- Specify the pathname of an alternate log socket to be used instead; the default is /var/run/log.
-P
- Specify an alternative file in which to store the process ID. The default is /var/run/syslog.pid.
-S
- Specify the pathname of an alternate log socket for privileged applications to be used instead; the default is /var/run/logpriv.
-l
- Specify a location where
syslogd
should place an additional log socket. The primary use for this is to place additional log sockets in /var/run/log of various chroot filespaces. File permissions for socket can be specified in octal representation before socket name, delimited with a colon. Path to socket location must be absolute. -s
- Operate in secure mode. Do not log messages from remote machines. If specified twice, no network socket will be opened at all, which also disables logging to remote machines.
-T
- Always use the local time and date for messages received from the network, instead of the timestamp field supplied in the message by the remote host. This is useful if some of the originating hosts can't keep time properly or are unable to generate a correct timestamp.
-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
utility 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
utility reads messages from
the UNIX domain sockets
/var/run/log and
/var/run/logpriv, from an Internet domain socket
specified in /etc/services, and from the special
device /dev/klog (to read kernel messages).
The syslogd
utility creates its process ID
file, by default /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>
.
For security reasons, syslogd
will not
append to log files that do not exist (unless -C
option is specified); therefore, they must be created manually before
running syslogd
.
The date and time are taken from the received message. If the
format of the timestamp field is incorrect, time obtained from the local
host is used instead. This can be overridden by the
-T
flag.
FILES
- /etc/syslog.conf
- configuration file
- /var/run/syslog.pid
- default process ID file
- /var/run/log
- name of the UNIX domain datagram log socket
- /var/run/logpriv
- UNIX socket for privileged applications
- /dev/klog
- kernel log device
SEE ALSO
logger(1), syslog(3), services(5), syslog.conf(5), newsyslog(8)
HISTORY
The syslogd
utility 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 does not pretend
to be very efficient; use of numeric IP addresses is faster than domain name
comparison. 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 file system. This may confuse some old binaries so that a symbolic link might be used for a transitional period.