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
persistent name
>>> 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:
cat /etc/kdump.conf
#raw /dev/vg/lv_kdump
#ext4 /dev/vg/lv_kdump
#xfs /dev/mapper/rhel-root
#ext4 UUID=03138356-5e61-4ab3-b58e-27507ac41937
#nfs 10.66.129.115:/export/nfs
#ssh user(a)my.server.com
#sshkey /root/.ssh/kdump_id_rsa
path /var/crash
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.
Regards,
Xunlei
~Pratyush