Solaris 10 massive SMF log file Post: 302845099

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Operating Systems Solaris Solaris 10 massive SMF log file Post 302845099 by achenle on Tuesday 20th of August 2013 09:06:01 PM

08-20-2013

Registered User

Quote:

Originally Posted by bartus11

You already know how:

Code:

cat /dev/null > /path/to/logfile

This will zero the file without interrupting any processes that had it open.

That's not guaranteed to work.

Depending on how the file was opened, how it's written to, and the specifics of how the underlying file system handles attempts to write past the end of a file, you could wind up doing nothing more than creating a file every bit as large as it was, only whatever data that was in the file is lost.

Here's what happens:

1. A process has an open file descriptor on a file, and the file was not opened in "append" mode.
2. File is truncated to zero bytes by an outside process.
Note that file descriptors have a "current" offset associated with them, and operations outside the process do not effect that position.
3. The process writes to the file, and the bytes go to the original pre-truncation "current" offset in the file.
4. If the underlying file system does not support sparse files, it's back to being 19GB. If the file system does support sparse files, an "ls -l" will still show the file as being 19 GB, but a "du" will show that the file actually uses much less space.

And all bets are off if a process has a file memory-mapped and the file is truncated out from under the mapping. Just try truncating a binary executable when a copy of that binary is running....

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doveadm-log

DOVEADM-LOG(1)							      Dovecot							    DOVEADM-LOG(1)

NAME

       doveadm-log - Locate, test or reopen Dovecot's log files

SYNOPSIS

       doveadm [-Dv] log errors
       doveadm [-Dv] log find [directory]
       doveadm [-Dv] log reopen
       doveadm [-Dv] log test

DESCRIPTION

       The  doveadm  log commands are used to locate and reopen the log files of dovecot(1).  It's also possible to test the configured targets of
       the *log_path settings.

OPTIONS

       Global doveadm(1) options:

       -D     Enables verbosity and debug messages.

       -v     Enables verbosity, including progress counter.

COMMANDS

   log errors
       doveadm log errors

       The log errors command is used to show the last	- up to 1,000 - errors and warnings.  If no output is generated, no errors  have  occurred
       since the last start.

   log find
       doveadm log find [directory]

       The  log  find  command	is used to show the location of the log files, to which dovecot(1) sends its log messages.  If dovecot(1) logs its
       messages through syslogd(8) and doveadm(1) could not find any log files, you can specify the directory where your syslogd  writes  its  log
       files.

   log reopen
       doveadm log reopen

       This command causes doveadm to reopen all log files, configured in the log_path, info_log_path and debug_log_path settings.  These settings
       are configured in /etc/dovecot/conf.d/10-logging.conf.
       This is for example useful after manually rotating the log files.

   log test
       doveadm log test

       This command causes doveadm to write the message "This is Dovecot's priority log (timestamp)" to the configured log files.  The used prior-
       ities are: debug, info, warning, error and fatal.

EXAMPLE

       This example shows how to locate the log files used by dovecot(1).

       doveadm log find
       Looking for log files from /var/log
       Debug: /var/log/dovecot.debug
       Info: /var/log/mail.log
       Warning: /var/log/mail.log
       Error: /var/log/mail.log
       Fatal: /var/log/mail.log

REPORTING BUGS

       Report  bugs,  including doveconf -n output, to the Dovecot Mailing List <dovecot@dovecot.org>.	Information about reporting bugs is avail-
       able at: http://dovecot.org/bugreport.html

SEE ALSO

       doveadm(1)

Dovecot v2.1							    2012-02-22							    DOVEADM-LOG(1)