[CentOS] secure file not updating

Mike -- EMAIL IGNORED m_d_berger_1900 at yahoo.com
Mon Dec 15 02:25:28 UTC 2008


On Sun, 14 Dec 2008 20:47:36 -0500, Filipe Brandenburger wrote:

> Hi,
> 
> On Sun, Dec 14, 2008 at 15:26, Mike -- EMAIL IGNORED
> <m_d_berger_1900 at yahoo.com> wrote:
>> If I do a vi on the secure file and write it from vi, it stops
>> recording.
> 
> Yes, that's the expected behaviour, because "vi" will actually write a
> new file and rename it to /var/log/secure, so syslog will no longer be
> writing to that file.
> 
> The file syslog is now writing to is not accessible on the filesystem
> (unless you created a hardlink to it before), but other processes that
> had it open before you saved it with "vi" will continue using the old
> one.
> 
>> If I do a "/var/init.d/syslog restart", the secure file starts
>> recording.
> 
> Yes, because syslog will open the new file again, by it's name, now it's
> the file "vi" wrote. Actually, when you stop syslog (and all other
> processes that had the old file open) it will be effectively deleted,
> but not before that.
> 
>> I still have no idea how swatch continues to function after the syslog
>> stops recording.
> 
> I'm not familiar with swatch, so I cannot say how it interacts with
> files that are written/renamed as you described with "vi".
> 
> If it's a "daemon" that is running on background all the time, chances
> are it will keep the file open (although not necessarily), so in this
> case it will "see" the new entries from syslog. If it's run from cron at
> fixed intervals, it will open the file every time it runs, so chances
> are if you rewrite the file with "vi" it will no longer see the new
> entries from syslog.
> 
> In any case, opening a logfile with "vi" is a bad idea, you should use a
> more appropriate tool such as "less", or if you really want to use "vi"
> commands, use "vi -R" or "view" for read-only mode.
> 
> HTH,
> Filipe

Very interesting analysis.  swatch uses tail -f, or something
that mimics it to watch the file.  I would then guess that as
per your explanation, swatch contilues to watch the "old file".

Mike.




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