how to rotate a tcpdump file
frank at shute.org.uk
Sat May 23 20:04:30 UTC 2009
On Sat, May 23, 2009 at 08:52:14PM +0100, Frank Shute wrote:
> On Sat, May 23, 2009 at 07:26:37PM +0200, Morgan Wesstrm wrote:
> > Frank Shute wrote:
> > > On Sat, May 23, 2009 at 02:57:08PM +0300, Yavuz Ma?lak wrote:
> > >> I wish tcpdump to rotate tcpdump file whose size reaches 10Mbyte.
> > >>
> > >> Which command should I use ?
> > >>
> > >
> > > You should be able to set up newsyslog(8) to rotate the dumps.
> > >
> > > You want to have a look at newsyslog.conf(5) to craft a line to put in
> > > your conf file. There are examples to work from in the conf file
> > > already.
> > >
> > > Regards,
> > Correct me if I'm wrong but wouldn't tcpdump have to be restarted after
> > the logrotate? I'm under the impression that it would just continue to
> > output to the old inode even if the file occupying it changes name and
> > the restart functionality of newsyslog(8) isn't really bright enough to
> > restart tcpdump with all its initial parameters.
> I was thinking of using the -C and -w options to tcpdump(1). From the
> -C Before writing a raw packet to a savefile, check whether the
> file is currently larger than file_size and, if so, close the
> current savefile and open a new one. Savefiles after the first
> savefile will have the name specified with the -w flag, with a
> number after it, starting at 1 and continuing upward. The units
> of file_size are millions of bytes (1,000,000 bytes, not
> 1,048,576 bytes).
> and now looking at it more closely, you don't even have to use
> newsyslog. Just include the args: -C 10000000 -w my_tcpdump_log
Oops! should be: -C 10 -w my_tcpdump_log
I assume the OP is not too bothered whether it's megabytes or
mebibytes or whatever the hell they call them (using base 10 rather
> You would still need a script to rotate the logs though.
> Probably, wrap tcpdump in a shell script that does some arithmetic
> similar to what Matthew has written in his post.
> > I'm using sysutils/cronolog for my Apache logs so I don't have to
> > restart Apache at all for the logrotate. Unfortunately cronolog doesn't
> > seem to have a size option to trigger the rotation though.
> You can use newsyslog with Apache to rotate logs. From my conf:
> /var/log/httpd-access.log 644 5 200 * B /var/run/httpd.pid 30
> 5 logfiles, 200Kb big, give Apache a SIGUSR1 (30) to stop & restart
> the logging.
> > Maybe there's another alternative for the OP?
> > /Morgan
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