On Sun, Mar 10, 2019 at 10:58 PM Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote: > > Normally 'btrfs rescue super' should be enough for accidentally wiped btrfs. > > If not, then we should fix it of course. Looks like a bug then. $ sudo mkfs.btrfs /dev/mapper/vg-f30test btrfs-progs v4.20.2 See http://btrfs.wiki.kernel.org for more information. Label: (null) UUID: e819e675-a697-45f8-8351-d109d5b95514 Node size: 16384 Sector size: 4096 Filesystem size: 100.00GiB Block group profiles: Data: single 8.00MiB Metadata: DUP 1.00GiB System: DUP 8.00MiB SSD detected: no Incompat features: extref, skinny-metadata Number of devices: 1 Devices: ID SIZE PATH 1 100.00GiB /dev/mapper/vg-f30test $ sudo mount /dev/mapper/vg-f30test /mnt/test $ sudo umount /mnt/test $ sudo wipefs -a /dev/mapper/vg-f30test /dev/mapper/vg-f30test: 8 bytes were erased at offset 0x00010040 (btrfs): 5f 42 48 52 66 53 5f 4d $ sudo btrfs rescue super -v /dev/mapper/vg-f30test No valid Btrfs found on /dev/mapper/vg-f30test Usage or syntax errors $ echo "_BHRfS_M" | sudo dd bs=1 count=8 of=/dev/mapper/vg-f30test seek=$((64*1024+64)) 8+0 records in 8+0 records out 8 bytes copied, 0.00523996 s, 1.5 kB/s $ sudo btrfs rescue super -v /dev/mapper/vg-f30test All Devices: Device: id = 1, name = /dev/mapper/vg-f30test Before Recovering: [All good supers]: device name = /dev/mapper/vg-f30test superblock bytenr = 65536 device name = /dev/mapper/vg-f30test superblock bytenr = 67108864 [All bad supers]: All supers are valid, no need to recover $ -- Chris Murphy
