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svlogd(8) System Manager's Manual svlogd(8)
NAME
svlogd - runit's service logging daemon
SYNOPSIS
svlogd [-tttv] [-r c] [-R xyz] [-l len] [-b buflen] logs
DESCRIPTION
logs consists of one or more arguments, each specifying a directory.
svlogd continuously reads log data from its standard input, optionally filters log mes-
sages, and writes the data to one or more automatically rotated logs.
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 be-
low.
LOG DIRECTORY
A log directory log contains some number of old log files, and the current log file cur-
rent. 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 @time-
stamp.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
PROCESSOR
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 out-
put 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.
CONFIG
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 ad-
justs configuration for log as follows:
If the line is empty, or starts with a ``#'', it is ignored. A line of the form
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.
ttimeout
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 rotation.
!processor
tells svlogd to feed each recent log file through processor (see above) on log file
rotation. By default log files are not processed.
ua.b.c.d[:port]
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 sys-
log 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. Atten-
tion: logging through udp is unreliable, and should be used in private networks
only.
Ua.b.c.d[:port]
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 con-
cerning sending udp packages still go to the log directory.
pprefix
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:
-pattern
the log message is deselected.
+pattern
the log message is selected.
epattern
the log message is selected to be printed to standard error.
Epattern
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.
PATTERN MATCHING
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 log message.
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
-*pid*
because the first star matches up to the first p in tcpsvd, and then the match fails be-
cause i is not s. To match this log message, you can use a pattern like this instead
-*: *: pid *
OPTIONS
-t timestamp. Prefix each selected line with a precise timestamp (see the daemon-
tools' tai64n program) when writing to log or to standard error.
-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.
-b buflen
buffer size. Set the size of the buffer svlogd uses when reading from standard in-
put 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.
SIGNALS
If svlogd is sent a HUP signal, it closes and reopens all logs, and updates their configu-
ration 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 directo-
ries 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 subpro-
cesses 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.
SEE ALSO
sv(8), runsv(8), chpst(8), runit(8), runit-init(8), runsvdir(8), runsvchdir(8)
http://smarden.org/runit/
AUTHOR
Gerrit Pape <pape AT smarden.org>
svlogd(8)
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On Apache
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