Thanks a lot. Seetharam > -----Original Message----- > From: nhorman at redhat.com > Sent: Tue, 16 Jun 2009 07:24:25 -0400 > To: dseetharam at inbox.com > Subject: Re: /var/log/messages doesn't have crash info when kernel gets > panic/oops/crash > > On Mon, Jun 15, 2009 at 08:43:02PM -0800, Dharmosoth Seetharam wrote: >> Hi, >> >> I have experimented few things and results are below. >> >> Case 1) echo 0 > /proc/sys/kernel/panic_on_oops >> When BUG/oops occurred it is able to log the diagnostics to >> /var/log/messages >> and then continue(not switching to dump-saving kernel). >> >> What I am looking is - I want both the things to be happen. >> that is - it should log the appropriate messages in >> /var/log/messsages and >> should be able to take kernel dump. >> >> case 2) In general, When panic has occurred we won't log any type of >> messages in >> /var/log/messages ... am I right ? >> If KEXEC is enabled and dump-saving kernel is loaded then >> will switch to it and save the kernel dump. >> >> I have added the dump_stack() function call in the panic() >> function >> before calling crash_kexec with few seconds of delay. It is >> behaving >> like randomly (ie. some time stack traces are logged in >> /var/log/messages and >> not for rest of the time) >> >> What I am looking is - I want to log the appropriate messages >> in /var/log/messages >> and then switch to dump-saving kernel. >> > Then what you want to do is, enable kdump, and set your kernel up to > panic_on_oops. Then, configure kdump to extract the dmesg log from > /proc/vmcore, and write that to a file (either a file you create, or to > the end > of /var/log/messages). Most distributions kdump configurations allow for > something simmilar to this. The new config method I've got in rawhide > should > make this very easy. > > The problem is that when you panic the box (which is what has to happen > for > kdump to start), the syslog daemon doesn't get a chance to run first, so > theres > no way to write the oops backtrace to var/log/messages. You'll need to > tell > kdump to do that for you after the fact. > >> case 3) In general, When die/nmi_die called we used to log the >> appropriate messages in /var/log/message >> and then saving kernel dump will be depends on KEXEC enable and >> loading dump-saving kernel. >> --- am I right ? >> >> I have added the delay in die() function with few seconds before >> calling crash_kexec() >> But I never seen messages logged in /var/log/messages, I can see >> those on serial console. >> > See above, when we printk those messages, klogd/syslogd needs to run to > get them > from the console buffer and write them to /var/log/messages. Theres no > guarantee that will ever happen. > >> Here also my intention is want both, ie. log the appropriate >> messages in /var/log/messages >> and then take the action as per KEXEC enabled. >> >> >> >> Please advice me, What we can do to achieve those things. >> > See above, use makedumpfile to extract the dmesg log from /proc/vmcore in > kdump, > then use a custom script to append the log to /var/log/messages. In > fedora that > will be equivalent to using the core_collector and kdump_post options in > /etc/kdump.conf. > > Neil > >> Thanks for helping me here. >> >> >> regards, >> Seetharam >> >> >> >> >> >>> -----Original Message----- >>> From: nhorman at redhat.com >>> Sent: Sat, 13 Jun 2009 14:07:36 -0400 >>> To: dseetharam at inbox.com >>> Subject: Re: /var/log/messages doesn't have crash info when kernel gets >>> panic/oops/crash >>> >>> On Fri, Jun 12, 2009 at 11:01:35PM -0800, Dharmosoth Seetharam wrote: >>>> >>>> Hi Neil, >>>> >>>> Thanks for your quick reply. >>>> >>>> What you have suggested is nice when we got/save crash dump (i.e >>>> vmcore) >>>> What if we failed to save/capture vmcore info or vmcore is corrupted >>>> etc. then we dont get any information >>>> regarding the panic/crash/oops at anywhere? >>>> >>> If the vmcore is corrupted to the point where makedumpfile can't >>> extract >>> the >>> dmesg log, then its certain that syslog wouldn't have been able to >>> write >>> anything to /var/log/messages either. As a last resort you can try run >>> strings >>> on the corrupted vmcore and see if the dmesg log is still in there >>> somewhere. >>> >>> If you forgot to capture the vmcore, theres not much more help I can >>> give >>> you, >>> Im afraid. You'll just have to make sure you capture it next time. If >>> you only >>> need the backtrace, and don't want the rest of the vmcore, you can make >>> kdump >>> just run makedumpfile --dump-dmesg /proc/vmcore /var/log/oops.txt >>> >>> Neil >>> >> >> >>>> >>>> >>>> >>>> Thanks and Regards >>>> >>>> Seetharam >>>> >>>> >>>>> -----Original Message----- >>>>> From: nhorman at redhat.com >>>>> Sent: Fri, 12 Jun 2009 16:05:13 -0400 >>>>> To: dseetharam at inbox.com >>>>> Subject: Re: /var/log/messages doesn't have crash info when kernel >>>>> gets >>>>> panic/oops/crash >>>>> >>>>> On Fri, Jun 12, 2009 at 01:25:49AM -0800, Dharmosoth Seetharam wrote: >>>>>> Hi, >>>>>> >>>>>> I have encounter a problem called /var/log/messages does not contain >>>>>> any >>>>>> information >>>>>> on kernel crash dump. >>>>>> >>>>>> Prior to enabling KEXEC we saw stack traces and bug info etc in >>>>>> /var/log/messages. >>>>>> After enabling KEXEC feature those info was missed. >>>>>> >>>>>> How can we get those missed info in /var/log/messages even when >>>>>> KEXEC >>>>>> feature is enabled. >>>>>> >>>>>> Any help will appreciate. >>>>>> >>>>> run crash on the resultant vmcore file that kexec can produce/save >>>>> and >>>>> get the >>>>> dmesg log out of it. >>>>> alternatively you can use makedumpfile with the --dump-dmesg log >>>>> >>>>> Neil >>>>> >>>>>> >>>>>> Thanks and Regards >>>>>> Seetharam >>>>>> >>>>>> ____________________________________________________________ >>>>>> Receive Notifications of Incoming Messages >>>>>> Easily monitor multiple email accounts & access them with a click. >>>>>> Visit http://www.inbox.com/notifier and check it out! >>>>>> >>>>>> _______________________________________________ >>>>>> kexec mailing list >>>>>> kexec at lists.infradead.org >>>>>> http://lists.infradead.org/mailman/listinfo/kexec >>>> >>>> ____________________________________________________________ >>>> GET FREE SMILEYS FOR YOUR IM & EMAIL - Learn more at >>>> http://www.inbox.com/smileys >>>> Works with AIM?, MSN? 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