svlogd - runit’s service logging daemon
svlogd [-tttv] [-r c] [-R xyz] [-l len] [-b buflen] logs
logs consists of one or more arguments, each specifying a directory.
svlogd continuously reads log data from its standard input, optionally
filters log messages, and writes the data to one or more automatically
Recent log files can automatically be processed by an arbitrary
processor program when they are rotated, and svlogd can be told to
alert selected log messages to standard error, and through udp.
svlogd runs until it sees end-of-file on standard input or is sent a
TERM signal, see below.
A log directory log contains some number of old log files, and the
current log file current. Old log files have a file name starting with
@ followed by a precise timestamp (see the daemontools’ tai64n
program), indicating when current was rotated and renamed to this file.
A log directory additionally contains the lock file lock, maybe state
and newstate, and optionally the file config. svlogd creates necessary
files if they don’t exist.
If svlogd has trouble opening a log directory, it prints a warning, and
ignores this log directory. If svlogd is unable to open all log
directories given at the command line, it exits with an error. This
can happen on start-up or after receiving a HUP signal.
LOG FILE ROTATION
svlogd appends selected log messages to the current log file. If
current has size bytes or more (or there is a new-line within the last
len of size bytes), or is older than a specified amount of time,
current is rotated:
svlogd closes current, changes permission of current to 0755, renames
current to @timestamp.s, and starts with a new empty current. If
svlogd sees num or more old log files in the log directory, it removes
the oldest one. Note that this doesn’t decrease the number of log
files if there are already more than num log files, this must be done
manually, e.g. for keeping 10 log files:
ls -1 \@* |sort |sed -ne ’10,$p’ |xargs rm
If svlogd is told to process recent log files, it saves current to
@timestamp.u, feeds @timestamp.u through ‘‘sh -c "processor"’’ and
writes the output to @timestamp.t. If the processor finishes
successfully, @timestamp.t is renamed to @timestamp.s, and @timestamp.u
is deleted; otherwise @timestamp.t is deleted and the processor is
started again. svlogd also saves any output that the processor writes
to file descriptor 5, and makes that output available on file
descriptor 4 when running processor on the next log file rotation.
A processor is run in the background. If svlogd sees a previously
started processor still running when trying to start a new one for the
same log, it blocks until the currently running processor has finished
successfully. Only the HUP signal works in that situation. Note that
this may block any program feeding its log data to svlogd.
On startup, and after receiving a HUP signal, svlogd checks for each
log directory log if the configuration file log/config exists, and if
so, reads the file line by line and adjusts configuration for log as
If the line is empty, or starts with a ‘‘#’’, it is ignored. A line of
ssize sets the maximum file size of current when svlogd should rotate
the current log file to size bytes. Default is 1000000. If
size is zero, svlogd doesn’t rotate log files. You should set
size to at least (2 * len).
nnum sets the number of old log files svlogd should maintain to num.
If svlogd sees more that num old log files in log after log file
rotation, it deletes the oldest one. Default is 10. If num is
zero, svlogd doesn’t remove old log files.
Nmin sets the minimum number of old log files svlogd should maintain
to min. min must be less than num. If min is set, and svlogd
cannot write to current because the filesystem is full, and it
sees more than min old log files, it deletes the oldest one.
sets the maximum age of the current log file when svlogd should
rotate the current log file to timeout seconds. If current is
timeout seconds old, and is not empty, svlogd forces log file
tells svlogd to feed each recent log file through processor (see
above) on log file rotation. By default log files are not
tells svlogd to transmit the first len characters of selected
log messages to the IP address a.b.c.d, port number port. If
port isn’t set, the default port for syslog is used (514). len
can be set through the -l option, see below. If svlogd has
trouble sending udp packets, it writes error messages to the log
directory. Attention: logging through udp is unreliable, and
should be used in private networks only.
is the same as the u line above, but the log messages are no
longer written to the log directory, but transmitted through udp
only. Error messages from svlogd concerning sending udp
packages still go to the log directory.
tells svlogd to prefix each line to be written to the log
directory, to standard error, or through UDP, with prefix.
If a line starts with a -, +, e, or E, svlogd matches the first len
characters of each log message against pattern and acts accordingly:
the log message is deselected.
the log message is selected.
the log message is selected to be printed to standard error.
the log message is deselected to be printed to standard error.
Initially each line is selected to be written to log/current.
Deselected log messages are discarded from log. Initially each line is
deselected to be written to standard err. Log messages selected for
standard error are written to standard error.
svlogd matches a log message against the string pattern as follows:
pattern is applied to the log message one character by one, starting
with the first. A character not a star (‘‘*’’) and not a plus (‘‘+’’)
matches itself. A plus matches the next character in pattern in the
log message one or more times. A star before the end of pattern
matches any string in the log message that does not include the next
character in pattern. A star at the end of pattern matches any string.
Timestamps optionally added by svlogd are not considered part of the
An svlogd pattern is not a regular expression. For example consider a
log message like this
2005-12-18_09:13:50.97618 tcpsvd: info: pid 1977 from 10.4.1.14
The following pattern doesn’t match
because the first star matches up to the first p in tcpsvd, and then
the match fails because i is not s. To match this log message, you can
use a pattern like this instead
-*: *: pid *
-t timestamp. Prefix each selected line with a precise timestamp
(see the daemontools’ tai64n program) when writing to log or to
-tt timestamp. Prefix each selected line with a human readable,
sortable UTC timestamp of the form YYYY-MM-DD_HH:MM:SS.xxxxx
when writing to log or to standard error.
-ttt timestamp. Prefix each selected line with a human readable,
sortable UTC timestamp of the form YYYY-MM-DDTHH:MM:SS.xxxxx
when writing to log or to standard error.
-r c replace. c must be a single character. Replace non-printable
characters in log messages with c. Characters are replaced
before pattern matching is applied.
-R xyz replace charset. Additionally to non-printable characters,
replace all characters found in xyz with c (default ‘‘_’’).
-l len line length. Pattern matching applies to the first len
characters of a log message only. Default is 1000.
buffer size. Set the size of the buffer svlogd uses when
reading from standard input and writing to logs to buflen.
Default is 1024. buflen must be greater than len. For svlogd
instances that process a lot of data in short time, the buffer
size should be increased to improve performance.
-v verbose. Print verbose messages to standard error.
If svlogd is sent a HUP signal, it closes and reopens all logs, and
updates their configuration according to log/config. If svlogd has
trouble opening a log directory, it prints a warning, and discards this
log directory. If svlogd is unable to open all log directories given
at the command line, it exits with an error.
If svlogd is sent a TERM signal, or if it sees end-of-file on standard
input, it stops reading standard input, processes the data in the
buffer, waits for all processor subprocesses to finish if any, and
exits 0 as soon as possible.
If svlogd is sent an ALRM signal, it forces log file rotation for all
logs with a non empty current log file.
sv(8), runsv(8), chpst(8), runit(8), runit-init(8), runsvdir(8),
Gerrit Pape <firstname.lastname@example.org>