Re: [libvirt] bug: try to take disk snapshot for LVM2 Volume

Sorry, I confirmed the snapshot file is not wrong. I moved the snapshot file created under /dev as /dev/VG1/abc.xxxxxx to other place and fixed the config file re-writed by libvirt to use moved snapshot file abc.xxxxxx. So, the domain starts with no problem. Regards MATSUDA Daiki

> On 11/15/2011 08:20 PM, Dave Allan wrote: >>> After working on this some more, I think that identifying problematic >>> file systems, like devtmpfs, is too tricky to be portable. But I >>> think >>> we can meet halfway - right now, the libvirt code blindly generates a >>> filename if one was not provided, regardless of the file type of the >>> backing file it will be wrapping. But maybe it would be sufficient to >>> make the command error out if no qcow2 filename is provided and the >>> backing file is not a regular file. As in this patch: >> >> Ok, now I understand the situation; thanks to everyone for the >> explanations. I'm somewhat uncomfortable using file type as a proxy >> for "troublesome filesystem" since although they are linked in this >> case, I'm not sure they're linked in all cases. Maybe I'm wrong about >> that. If there is no portable way to determine whether a particular >> filesystem is going to be a problem, I would just clearly document the >> limitations of letting libvirt choose the filename and the importance >> of not using that functionality on filesystems that cannot hold a >> useful snapshot. > > My patch would not be preventing snapshots of block devices, but merely > requiring that the user supply the qcow2 filename that will wrap the > block device. The problem with just documenting the issue is that > someone will fail to read the documentation, perform a default snapshot > that creates a problematic qcow2 file, then be upset that their domain > fails to boot and that they lost all the changes made since the > snapshot. I'm still in favor of this patch if anyone else thinks it is > worthwhile. > >>> Subject: [PATCH] snapshot: refuse to generate names for non-regular >>> backing >>> files >>> >>> For whatever reason, the kernel allows you to create a regular >>> file named /dev/sdc.12345; although this file will disappear the >>> next time devtmpfs is remounted. If you let libvirt generate >>> the name of the external snapshot for a disk image originally >>> using the block device /dev/sdc, then the domain will be rendered >>> unbootable once the qcow2 file is lost on the next devtmpfs >>> remount. In this case, the user should have used 'virsh >>> snapshot-create --xmlfile' or 'virsh snapshot-create-as --diskspec' >>> to specify the name for the qcow2 file in a sane location, rather >>> than relying on libvirt generating a name that is most likely to >>> be wrong. We can help avoid naive mistakes by enforcing that >>> the user provide the external name for any backing file that is >>> not a regular file. >>> >>> * src/conf/domain_conf.c (virDomainSnapshotAlignDisks): Only >>> generate names if backing file exists as regular file. >>> Reported by MATSUDA Daiki. > > > > -- > libvir-list mailing list > libvir-list(a)redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list