Re: [PATCH V2 3/3] kdumpctl: force rebuild in case of dump target modification

[Dave Young]

Hi, Pratyush

Seem one comment inline about variable quotation, otherwise I'm fine.

On 04/11/16 at 03:54pm, 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
>  re-formated.
>  kdumpctl must have a mechanism to recognise this modification, so that its
>  service restart is able to rebuild initramfs.
>  
>  Testing:
>  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" TYPE="ext4"
>  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&gt;
>  ---
>   kdumpctl | 38 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
>  
>  diff --git a/kdumpctl b/kdumpctl
>  index 614a816e344c..303626a276fe 100755
>  --- a/kdumpctl
>  +++ b/kdumpctl
>  @@ -327,10 +327,48 @@ setup_target_initrd()
>   	fi
>   }
>   
>  +is_dump_target_modified()
>  +{
>  +	local _target _dracut_args _uuid
>  +
>  +	_target=$(egrep "^ext[234]|^xfs|^btrfs" /etc/kdump.conf)
>  +
>  +	#if dump target does not exist then do not rebuild
>  +	[[ -n "$_target" ]] || return 0
>  +
>  +	_dracut_args=$(lsinitrd $TARGET_INITRD | grep "^Arguments:" | head -1)
>  +	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
>  +	[[ $? -eq 0 ]] || return 0
>  +
>  +	_target=$(echo $_target | cut -d ' ' -f 2)
>  +	_uuid=$(blkid $_target | awk -F"UUID=" '{print $2}' | cut -d
> '"' -f 2)
>  +	if [[ -z $_uuid ]];then 
quote $_uuid

>  +		echo "Warning: UUID is not present"
>  +		return 1
>  +	fi
>  +
>  +	echo $_dracut_args  | grep $_uuid &> /dev/null
>  +	#if dracut argument and _target have same uuid, then also do not rebuild
>  +	[[ $? -ne 0 ]] || return 0
>  +
>  +	return 1
>  +}
>  +
>   is_system_modified()
>   {
>   	[[ -f $TARGET_INITRD ]] || return 1
>   
>  +	is_dump_target_modified
>  +	if [ $? -ne 0 ]; then
>  +	        echo "Detected change in dump target"
>  +	        return 1
>  +	fi
>  +
>   	return 0
>   }
>   
>  -- 
>  2.5.0
>  _______________________________________________
>  kexec mailing list
>  kexec(a)lists.fedoraproject.org
>  http://lists.fedoraproject.org/admin/lists/[e-mail] 
Thanks
Dave