Re: Copying a disk containing a btrfs filesystem
Dne Čt 10. dubna 2014 15:21:01, Michael Schuerig napsal(a): SMART indicates that my notebook disk may soon be failing (an unreadable/uncorrectable sector), therefore I intend to exchange it. The disk contains a single btrfs filesystem with several nested(!) subvolumes, each with several read-only snapshots in a .snapshots subdirectory. As far as I can tell, btrfs currently does not offer a sensible way to duplicate the entire contents of the old disk onto a new one. Yes it does You can make the old disk a seeding device and use it to seed the new one like this: btrfstune -S 1 old_device mount old_device /mnt # this will be mounted read-only btrfs dev add new_device /mnt mount -o remount,rw /mnt btrfs dev delete old_device According to my experiments, the filesystem on the new device will have different UUID, so if you are mounting using UUIDs, you must change it everywhere, but other than that the new filesystem should have the same content as the old one (including subvolumes). I can use cp, rsync, or send/receive to copy the main subvolumes. But unless I'm missing something obvious, the snapshots are effectively lost. btrfs send optionally takes multiple clone sources, but I've never seen an example of its usage. If that's what experimental means, I'm willing to accept it. However, I'd like to emphasize that there's still something missing. Of course, most of all I'd like to be proved wrong. Michael -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Copying a disk containing a btrfs filesystem
Dne Čt 10. dubna 2014 20:36:32, Michael Schuerig napsal(a): On Thursday 10 April 2014 19:17:13 Jan Kouba wrote: Dne Čt 10. dubna 2014 15:21:01, Michael Schuerig napsal(a): SMART indicates that my notebook disk may soon be failing (an unreadable/uncorrectable sector), therefore I intend to exchange it. The disk contains a single btrfs filesystem with several nested(!) subvolumes, each with several read-only snapshots in a .snapshots subdirectory. As far as I can tell, btrfs currently does not offer a sensible way to duplicate the entire contents of the old disk onto a new one. Yes it does You can make the old disk a seeding device and use it to seed the new one like this: Intriguing. I didn't find much on the topic, but these pages seem pertinent http://en.wikipedia.org/wiki/Btrfs#Seed_devices https://btrfs.wiki.kernel.org/index.php/Seed-device http://unix.stackexchange.com/a/97819/64935 btrfstune -S 1 old_device Does the 1 mean true or is this indeed an integer-value arg? I've only seen the 1 in examples, are there other possible values? Yes, 1 means true, 0 false. If you run it twice with the same argument, it says something like Seeding flag already set/unset.. mount old_device /mnt # this will be mounted read-only btrfs dev add new_device /mnt mount -o remount,rw /mnt btrfs dev delete old_device Is the last one the step where data is copied from the seed device to the second device? No balance required before deleting the device? Yes, everything is copied, no balance needed. Well actually if you don't need to preserve the filesystem on the old device, you can just add the new device into the filesystem and remove the old one like this: mount old_device /mnt btrfs dev add new_device /mnt btrfs dev delete old_device /mnt The last command will copy everything from old_device to the new_device and somehow wipe the old_device so it can't be mounted anymore. This method will also preserve the UUID of the filesystem so there is no need to change any config files. Jan Kouba -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Unable to remove read-only seeding device from a filesystem.
When running this script: dd if=/dev/zero of=seed-disk.img bs=1M seek=1k count=0 dd if=/dev/zero of=test-disk.img bs=1M seek=1k count=0 # Make image of seed device mkfs.btrfs seed-disk.img seed_dev=`losetup -f --show seed-disk.img` mount $seed_dev /mnt/tmp touch /mnt/tmp/a umount /mnt/tmp losetup -d $seed_dev btrfstune -S 1 seed-disk.img # Make read-only seed device seed_dev=`losetup -f -r --show seed-disk.img` test_dev=`losetup -f --show test-disk.img` mount $seed_dev /mnt/tmp btrfs dev add $test_dev /mnt/tmp mount -o remount,rw /mnt/tmp # This fails btrfs dev delete $seed_dev /mnt/tmp # cleanup umount /mnt/tmp losetup -d $seed_dev losetup -d $test_dev rm seed-disk.img rm test-disk.img the command btrfs dev delete $seed_dev /mnt/tmp fails with ERROR: error removing the device '/dev/loop0' - Permission denied message. If /dev/loop0 is not read-only everything works. I tested this on ubuntu 13.10, 14.04 with stock kernel and btrfs-progs and on ubuntu 14.04 with latest PPA kernel (3.14.0-031400-generic) and v3.14 btrfs- progs. Is this behaviour expected or is it a bug? I thougt that btrfs never changes seeding devices, so I don't understand, why it needs to be writeable in order to remove it from a filesystem. Jan Kouba -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
