On 2016/04/27 at 17:23, Pratyush Anand wrote:
Thanks for the review.
On Wed, Apr 27, 2016 at 2:28 PM, Xunlei Pang <xpang(a)redhat.com> wrote:
> On 2016/04/20 at 18:07, Pratyush Anand wrote:
>> kdump also passes persistent device mapping as --mount or --device argument
>> of dracut. However this persistent id (UUID) is changed if dump target is
>> kdumpctl must have a mechanism to recognise this modification, so that its
>> service restart is able to rebuild initramfs.
>> a) Attach an IDE device, lets say it is /dev/sdb1
>> b) Format it as ext4
>> # mkfs.ext4 /dev/sdb1
>> # blkid /dev/sdb1
>> /dev/sdb1: UUID="21c7baff-e35d-49c7-aa08-0fba4513f5bf"
>> c) Mount it into /mnt and create a var/crash directory in it.
>> # mount /dev/sdb1 /mnt;mkdir /mnt/var;mkdir /mnt/var/crash
>> d) Add following line in /etc/kdump.conf
>> ext4 /dev/sdb1
>> e) Restart kdumpctl
>> # kdumpctl restart
>> f) crash
>> # echo c > /proc/sysrq-trigger
>> g) Here you will be able save vmcore with or without this patch.
>> h) repeat step (b), (c), (e) and (f)
>> i) Now you will be able to save vmcore only when you have this patch in
>> your kexec-tools. Your initramfs will be rebuilt when you repeat step (e)
>> after reformatting.
>> Signed-off-by: Pratyush Anand <panand(a)redhat.com>
>> kdumpctl | 39 +++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 39 insertions(+)
>> diff --git a/kdumpctl b/kdumpctl
>> index 1cba00b9dc0f..f7e3af8733f5 100755
>> --- a/kdumpctl
>> +++ b/kdumpctl
>> @@ -359,6 +359,39 @@ is_files_modified()
>> return 0
>> + local _target _dracut_args _uuid
>> + _target=$(egrep "^ext|^xfs|^btrfs" /etc/kdump.conf)
>> + #if dump target does not exist then do not rebuild
>> + [[ -n "$_target" ]] || return 0
>> + _dracut_args=$(lsinitrd $TARGET_INITRD | grep "^Arguments:" |
>> + if [[ -z "$_dracut_args" ]];then
>> + echo "Warning: No dracut arguments found in initrd"
>> + return 0
>> + fi
>> + #if --mount or --device is not by UUID, then also do not rebuild
>> + echo $_dracut_args | grep "by-uuid" &> /dev/null
>> + [[ $? -eq 0 ]] || return 0
> May be "[[ $? -ne 0 ]] && return 0" is more readable, but
that's ok :-)
OK..Will use above format from next time.
> Additionally, for device mappers, if they got reformatted, because the persistent
> 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?