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Top Forums Shell Programming and Scripting Log rotation issue with script Post 302472637 by navinmistry on Wednesday 17th of November 2010 05:36:13 PM
Old 11-17-2010
Log rotation issue with script

I have application which to the heavy stdout and I have diverted the stdout to log file.

this log file is writing very heavily and we have a script which rotates the logs.
logic for rotation is smthing like
cp logfile logfile.1
cat /dev/null > logfile

this logic was working fine till we had lesser load coming in logfile but Now there is much stdout going on and after doing a
cat /dev/null > logfile

logfile becomes of size 0 but again shows the same size as was it before.


so what I'm having is
logfile 1GB
after rotation
logfile.1 1GB
logfile 1GB & still appending the data.


I see the FD 1 for the log write is showing the same size as of the file and not coming down.

can you see any issue with this kind of log rotation why it is breaking on heavy IO ( my assumption is that FD 1 is still in blocking mode )
and any suggestion how it can be solved by scripting or othere logic/commands.


Thanks..
Navin
 

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LOGROTATE(8)						   System Administrator's Manual					      LOGROTATE(8)

NAME
logrotate - rotates, compresses, and mails system logs SYNOPSIS
logrotate [-dv] [-f|--force] [-s|--state file] config_file+ DESCRIPTION
logrotate is designed to ease administration of systems that generate large numbers of log files. It allows automatic rotation, compres- sion, removal, and mailing of log files. Each log file may be handled daily, weekly, monthly, or when it grows too large. Normally, logrotate is run as a daily cron job. It will not modify a log multiple times in one day unless the criterium for that log is based on the log's size and logrotate is being run multiple times each day, or unless the -f or -force option is used. Any number of config files may be given on the command line. Later config files may override the options given in earlier files, so the order in which the logrotate config files are listed in is important. Normally, a single config file which includes any other config files which are needed should be used. See below for more information on how to use the include directive to accomplish this. If a directory is given on the command line, every file in that directory is used as a config file. If no command line arguments are given, logrotate will print version and copyright information, along with a short usage summary. If any errors occur while rotating logs, logrotate will exit with non-zero status. OPTIONS
-d Turns on debug mode and implies -v. In debug mode, no changes will be made to the logs or to the logrotate state file. -f, --force Tells logrotate to force the rotation, even if it doesn't think this is necessary. Sometimes this is useful after adding new entries to logrotate, or if old log files have been removed by hand, as the new files will be created, and logging will continue correctly. -m, --mail <command> Tells logrotate which command to use when mailing logs. This command should accept two arguments: 1) the subject of the message, and 2) the recipient. The command must then read a message on standard input and mail it to the recipient. The default mail command is /bin/mail -s. -s, --state <statefile> Tells logrotate to use an alternate state file. This is useful if logrotate is being run as a different user for various sets of log files. The default state file is /var/lib/logrotate/status. --usage Prints a short usage message. CONFIGURATION FILE
logrotate reads everything about the log files it should be handling from the series of configuration files specified on the command line. Each configuration file can set global options (local definitions override global ones, and later definitions override earlier ones) and specify a logfile to rotate. A simple configuration file looks like this: # sample logrotate configuration file compress /var/log/messages { rotate 5 weekly postrotate /sbin/killall -HUP syslogd endscript } "/var/log/httpd/access.log" /var/log/httpd/error.log { rotate 5 mail www@my.org size=100k sharedscripts postrotate /sbin/killall -HUP httpd endscript } /var/log/news/news.crit { monthly rotate 2 olddir /var/log/news/old missingok postrotate kill -HUP `cat /var/run/inn.pid` endscript nocompress } The first few lines set global options; in the example, logs are compressed after they are rotated. Note that comments may appear anywhere in the config file as long as the first non-whitespace character on the line is a #. The next section of the config files defined how to handle the log file /var/log/messages. The log will go through five weekly rotations before being removed. After the log file has been rotated (but before the old version of the log has been compressed), the command /sbin/killall -HUP syslogd will be executed. The next section defines the parameters for both /var/log/httpd/access.log and /var/log/httpd/error.log. They are rotated whenever is grows over 100k is size, and the old logs files are mailed (uncompressed) to www@my.org after going through 5 rotations, rather then being removed. The sharedscripts means that the postrotate script will only be run once, not once for each log which is rotated. Note that the double quotes around the first filename at the beginning of this section allows logrotate to rotate logs with spaces in the name. Normal shell quoting rules apply, with ', ", and characters supported. The last section defines the parameters for all of the files in /var/log/news. Each file is rotated on a monthly basis. This is considered a single rotation directive and if errors occur for more then one file, the log files are not compressed. Please use wildcards with caution. If you specify *, logrotate will rotate all files, including previously rotated ones. A way around this is to use the olddir directive or a more exact wildcard (such as *.log). Here is more information on the directives which may be included in a logrotate configuration file: compress Old versions of log files are compressed with gzip by default. See also nocompress. compresscmd Specifies which command to use to compress log files. The default is gzip. See also compress. uncompresscmd Specifies which command to use to uncompress log files. The default is gunzip. compressext Specifies which extension to use on compressed logfiles, if compression is enabled. The default follows that of the configured com- pression command. compressoptions Command line options may be passed to the compression program, if one is in use. The default, for gzip, is "-9" (maximum compres- sion). copy Make a copy of the log file, but don't change the original at all. This option can be used, for instance, to make a snapshot of the current log file, or when some other utility needs to truncate or pare the file. When this option is used, the create option will have no effect, as the old log file stays in place. copytruncate Truncate the original log file in place after creating a copy, instead of moving the old log file and optionally creating a new one, It can be used when some program can not be told to close its logfile and thus might continue writing (appending) to the previous log file forever. Note that there is a very small time slice between copying the file and truncating it, so some logging data might be lost. When this option is used, the create option will have no effect, as the old log file stays in place. create mode owner group Immediately after rotation (before the postrotate script is run) the log file is created (with the same name as the log file just rotated). mode specifies the mode for the log file in octal (the same as chmod(2)), owner specifies the user name who will own the log file, and group specifies the group the log file will belong to. Any of the log file attributes may be omitted, in which case those attributes for the new file will use the same values as the original log file for the omitted attributes. This option can be disabled using the nocreate option. daily Log files are rotated every day. delaycompress Postpone compression of the previous log file to the next rotation cycle. This has only effect when used in combination with com- press. It can be used when some program can not be told to close its logfile and thus might continue writing to the previous log file for some time. extension ext Log files are given the final extension ext after rotation. If compression is used, the compression extension (normally .gz) appears after ext. ifempty Rotate the log file even if it is empty, overiding the notifempty option (ifempty is the default). include file_or_directory Reads the file given as an argument as if it was included inline where the include directive appears. If a directory is given, most of the files in that directory are read in alphabetic order before processing of the including file continues. The only files which are ignored are files which are not regular files (such as directories and named pipes) and files whose names end with one of the taboo extensions, as specified by the tabooext directive. The include directive may not appear inside of a log file definition. mail address When a log is rotated out-of-existence, it is mailed to address. If no mail should be generated by a particular log, the nomail directive may be used. mailfirst When using the mail command, mail the just-rotated file, instead of the about-to-expire file. maillast When using the mail command, mail the about-to-expire file, instead of the just-rotated file (this is the default). missingok If the log file is missing, go on to the next one without issuing an error message. See also nomissingok. monthly Log files are rotated the first time logrotate is run in a month (this is normally on the first day of the month). nocompress Old versions of log files are not compressed with gzip. See also compress. nocopy Do not copy the original log file and leave it in place. (this overrides the copy option). nocopytruncate Do not truncate the original log file in place after creating a copy (this overrides the copytruncate option). nocreate New log files are not created (this overrides the create option). nodelaycompress Do not postpone compression of the previous log file to the next rotation cycle (this overrides the delaycompress option). nomail Don't mail old log files to any address. nomissingok If a log file does not exist, issue an error. This is the default. noolddir Logs are rotated in the same directory the log normally resides in (this overrides the olddir option). nosharedscripts Run prerotate and postrotate scripts for every script which is rotated (this is the default, and overrides the sharedscripts option). notifempty Do not rotate the log if it is empty (this overrides the ifempty option). olddir directory Logs are moved into directory for rotation. The directory must be on the same physical device as the log file being rotated. When this option is used all old versions of the log end up in directory. This option may be overriden by the noolddir option. postrotate/endscript The lines between postrotate and endscript (both of which must appear on lines by themselves) are executed after the log file is rotated. These directives may only appear inside of a log file definition. See prerotate as well. prerotate/endscript The lines between prerotate and endscript (both of which must appear on lines by themselves) are executed before the log file is rotated and only if the log will actually be rotated. These directives may only appear inside of a log file definition. See postro- tate as well. firstaction/endscript The lines between firstaction and endscript (both of which must appear on lines by themselves) are executed once before all log files that match the wildcarded pattern are rotated, before prerotate script is run and only if at least one log will actually be rotated. These directives may only appear inside of a log file definition. See lastaction as well. lastaction/endscript The lines between lastaction and endscript (both of which must appear on lines by themselves) are executed once after all log files that match the wildcarded pattern are rotated, after postrotate script is run and only if at least one log is rotated. These direc- tives may only appear inside of a log file definition. See lastaction as well. rotate count Log files are rotated <count> times before being removed or mailed to the address specified in a mail directive. If count is 0, old versions are removed rather then rotated. size size Log files are rotated when they grow bigger then size bytes. If size is followed by M, the size if assumed to be in megabytes. If the k is used, the size is in kilobytes. So size 100, size 100k, and size 100M are all valid. sharedscripts Normally, prescript and postscript scripts are run for each log which is rotated, meaning that a single script may be run multiple times for log file entries which match multiple files (such as the /var/log/news/* example). If sharedscript is specified, the scripts are only run once, no matter how many logs match the wildcarded pattern. However, if none of the logs in the pattern require rotating, the scripts will not be run at all. This option overrides the nosharedscripts option. start count This is the number to use as the base for rotation. For example, if you specify 0, the logs will be created with a .0 extension as they are rotated from the original log files. If you specify 9, log files will be created with a .9, skipping 0-8. Files will still be rotated the number of times specified with the count directive. tabooext [+] list The current taboo extension list is changed (see the include directive for information on the taboo extensions). If a + precedes the list of extensions, the current taboo extension list is augmented, otherwise it is replaced. At startup, the taboo extension list contains .rpmorig, .rpmsave, ,v, .swp, .rpmnew, and ~. weekly Log files are rotated if the current weekday is less then the weekday of the last rotation or if more then a week has passed since the last rotation. This is normally the same as rotating logs on the first day of the week, but it works better if logrotate is not run every night. FILES
/var/lib/logrotate/status Default state file. /etc/logrotate.conf Configuration options. SEE ALSO
gzip(1) AUTHORS
Erik Troan <ewt@redhat.com> Preston Brown <pbrown@redhat.com> 4th Berkeley Distribution Wed Nov 5 2002 LOGROTATE(8)
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