On Tue, Apr 26, 2022 at 05:39:46PM +0800, Kairui Song wrote:
Coiby Xu <coxu(a)redhat.com> 于2022年4月25日周一 17:35写道:
>
> On Mon, Apr 25, 2022 at 04:55:03PM +0800, Kairui Song wrote:
> >Ok, thanks for the clarification.
>
> You are welcome!
>
> >
> [...]
> >> >
> >> >Just one concern, could there be any wired DHCP corner case? Like if
> >> >the kdump kernel took a longer time to boot, eg. 5 min, and then your
> >> >DHCP IP just expired during that time window, the kdump kernel will be
> >> >using an expired IP and conflict with other machines. The minimal
> >> >lease time of DHCP address is 1 hr, could be a rare corner case, but
> >> >in-theory possible.
> >>
> >> It seems I don't fully understand you. In the kdump kernel, we still
use
> >> DHCP to have a IP so there should be conflict. kdumpip is only used to
> >> create to a dumping folder named "{IP}-{DATE}" and we don't
assign
> >> kdumpip to a NIC.
> >
> >Oh, yes, you are right, I didn't read the patch carefully enough.
> >Since kdumpip is only used to create the dump dir, then this is fine.
> >
> >Now I'm a bit concerned that kdumpip being embedded inside the initramfs.
> >kdumpip could be dynamic, but the initramfs isn't. This is probably
> >okay? since it's only used to naming the dump dir...
> >
> >IIUC, now the dump dir's ip prefix could be out-of-sync with the
> >actual IP address of the machine when the dump happens, and will be in
> >out-of-sync status for a long time until the initramfs get rebuilt.
> >Just not sure if this will confuse anyone...
>
> Thanks for coming up with this scenario! I thought in the case where we
> have a different IP in the kdump kernel, the original IP of the 1st
> kernel can better tell us where the dump happens. But I haven't took
> the above scenario into consideration. How about we using FAQN i.e.
> `hostname --fqdn` and the date to name the dumping folder instead?
>
Looks like a solution, just one thing I'm not sure, is `hostname
--fqdn` unique enough? If a lot of VMs are installed using the same VM
image (very common in many cloud environment), and the VM image all
have a fixed hostname, all dump dirs could have the same prefix...
Thanks for raising this concern! In v1, kdump now tries to get {IP}
after booting the kdump initrd.
> --
> Best regards,
> Coiby
>
--
Best regards,
Coiby