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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LEARN ABOUT CENTOS

nislog

nislog(1M)                                                System Administration Commands                                                nislog(1M)

NAME

       nislog - display the contents of the NIS+ transaction log

SYNOPSIS

       /usr/sbin/nislog [-h num | -t num]  [-v] [directory...]

DESCRIPTION

       nislog  displays  the  contents of the NIS+ server transaction log on the standard output. This command can be used to track changes in the
       namespace. The /var/nis/trans.log file contains the transaction log maintained by the NIS+ server. When updates occur, they are  logged  to
       this  file  and  then  propagated  to replicas as log transactions.  When the log is checkpointed, updates that have been propagated to the
       replicas are removed.

       The nislog command can only be run on an NIS+ server by superuser. It displays the log entries for that server only.

       If directory is not specified, the entire log is searched. Otherwise, only those logs entries that correspond to the specified  directories
       are displayed.

OPTIONS

       -h num          Display num transactions from the ``head'' of the log. If the numeric parameter is  0, only the log header is displayed.

       -t num          Display  num transactions from the ``tail'' of the log. If the numeric parameter is  0, only the log header is displayed.

       -v              Verbose mode.

FILES

       /var/nis/trans.log      transaction log

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWnisu                     |
       +-----------------------------+-----------------------------+

SEE ALSO

       nis+(1), rpc.nisd(1M), nisfiles(4), attributes(5)

NOTES

       NIS+  might  not  be  supported in future releases of the SolarisTM Operating Environment. Tools to aid the migration from NIS+ to LDAP are
       available in the Solaris 9 operating environment. For more information, visit http://www.sun.com/directory/nisplus/transition.html.

SunOS 5.10                                                          12 Dec 2001                                                         nislog(1M)