On Wed, Apr 27, 2016 at 6:10 PM, Xunlei Pang <xpang(a)redhat.com> wrote:
On 2016/04/27 at 20:10, Pratyush Anand wrote:
> On Wed, Apr 27, 2016 at 4:56 PM, Xunlei Pang <xpang(a)redhat.com> wrote:
>> On 2016/04/27 at 17:23, Pratyush Anand wrote:
>>>> Additionally, for device mappers, if they got reformatted, because the
>>>> is from "/dev/mapper" not from "/dev/disk/by-uuid",
will "return 0" here, not rebuilt.
>>>> Should we handle this?
>>> we do not need to rebuild in that case. Persistent name would be valid
>>> and so dracut will create valid root mount point.
>> Yes, but if a device mapper device is reformatted to be a different filesystem,
>> its uuid is changed(after remount, its fstype changes), then user restart kdump,
>> shouldn't we trigger rebuilding to update its mount fstype passed to dracut?
> Yes, I agree if above could be a valid scenario then we need to
> rebuild in that case. I am not sure how to generate above scenario.
> If you can help with a scenario for generating above issue, I can
> cook a patch to resolve. Moreever, should we also not required to
> change the filesystem type in kdump.conf?
> This is what my understanding is:
> -- When we pass filesystem type and target device (like ext4
> /dev/sdb1) in kdump.conf, then kexec-tools passes --mount as
> '/dev/disk/by-uuid/...'. So, whenever we will reformat even with
> different filesystem, UUID will change and there will be a rebuild.
> -- If we do not pass filesystem type, but "dump path" (like
> /var/crash) mounts a device other than the device which mounts root,
> then also kexec-tools passes --mount as '/dev/disk/by-uuid/...'. So,
> in that case as well it will rebuild after reformatting.
> -- kexec-tools does not pass --mount or --device when both "dump
> path" and root path mounts same device.
For example, I just tested on my laptop:
Initailly it was mounted as:
/dev/mapper/rhel-swap on /var/crash type ext2 (rw,relatime,seclabel)
Then I unmounted /var/crash and changed /dev/mapper/rhel-swap to a ext4 using mkfs.ext4:
/dev/mapper/rhel-swap on /var/crash type ext4 (rw,relatime,seclabel,data=ordered)
After that, I did kdumpctl restart, it didn't trigger the rebuilding.
Actually, though "/dev/mapper/rhel-swap" device mapper name was not changed,
but its(dm-1's) uuid (and filesystem) has been changed.
Got It :-)
Thanks for the creating a scenario. Will send a follow-up patch to resolve it.