In Debian/Ubuntu, the samba packages include a logrotate chunk that allows logfiles (nmbd.log and smbd.log, which are the logfiles used by samba in the default setup) to be rotated weekly.

This is done with logrotate.

The entry for samba is:
/var/log/samba/log.smbd {
        weekly
        missingok
        rotate 7
        postrotate
                invoke-rc.d --quiet samba reload > /dev/null
        endscript
        compress
        notifempty
}

/var/log/samba/log.nmbd {
        weekly
        missingok
        rotate 7
        postrotate
                [ ! -f /var/run/samba/nmbd.pid ] || kill -HUP `cat /var/run/samba/nmbd.pid`
        endscript
        compress
        notifempty
}


However, our user in Debian bug #394770 noticed that smbd continues to write to the rotated file(s), named smbd.log.0, instead of writing to smbd.log

So, it seems that smbd does not close/reopen the logfile when stopped with SIGHUP.

Of course, I'm opened to any suggeston to improve this (except stop/start of the samba daemons when rotating the logfiles, of course)