Re: logs

[Paul DuBois]

At 3:09 PM -0500 2000-01-07, Charles Kirby wrote:
>If you do shut down mysqld, then you can do whatever you like, since
>it'll append if the log is there, and it'll create a new log file
>otherwise.
>Even if it IS running, I find there's no problem doing "cp /dev/null
>blah.com.log", since this will null out the file without affecting the
>file's i-node status.  This is the simplest solution I'd say.  If I want
>to save the file without stopping the daemon, I copy the log elsewhere
>(and later zip it), and then I can /dev/null it.  If there's activity
>while you're doing this, you'll lose some lines of log file.
>If you "mv" the log file... I notice the file will continue to be written
>to, regardless of the name of the file :)  Not a good method.
>
>ck


Actually, that is a good method, it just needs another step.  Under UNIX,
if a process has a file open, it will continue to be able to write to the
file , even if the file is renamed or removed.  That's because the name
just points to an inode (the underlying storage), and renaming/removing
doesn't affect the underlying storage.  Renaming just changes the name,
and removing just removes the pointer to the storage (the storage isn't
removed until the last pointer goes away *and* the file is closed).

You can use this behavior to your own advantage:

mv log log.0			# rename log file
mysqladmin flush-logs		# flush the log files

The flush-logs step will tell the server to close the log files and
reopen them.  Since you've renamed the original log file, the server
will open a new fresh file named "log" and you can then do whatever
you like the "log.0".

>
>On Fri, 7 Jan 2000 apocoliptica@stripped wrote:
>
>>  I noticed my mysql log file is getting fairly big.
>>  Does the mysqld have to be shut down prior to successfully deleting the log?
>>  Recalling the procedure for apache logs, I wanted to ask before acting...
>>
>>  Thanks,
>>  Apoc
>>
>>
>>
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-- 
Paul DuBois, paul@stripped