> So I did this: > > btrfs subvol snapshot /bkp /bkp/backup-subvol > > strangely while /bkp/backup has lots of files in it, > /bkp/backup-subvol/backup has none. > > # btrfs subvol list /bkp > ID 258 gen 313585 top level 5 path backup > ID 4782 gen 313590 top level 5 path backup-subvol OK so previously you said "/bkp which is a top level subvolume. There are no other subvolumes." But in fact backup is already a subvolume. So now it's confusing what you were asking for in the first place, maybe you didn't realize backup is not a dir but it is a subvolume. If you snapshot a subvolume, which itself contains subvolumes, the nested subvolumes are not snapshot. In the snapshot, the nested subvolumes are empty directories. > > # btrfs fi du -s /bkp/backup-subvol/backup > Total Exclusive Set shared Filename > ERROR: cannot check space of '/bkp/backup-subvol/backup': Inappropriate > ioctl for device That's a bug in older btrfs-progs. It's been fixed, but I'm not sure what version, maybe by 4.14? > > Any ideas about what could be going on? > > In the mean time I'm trying: > > btrfs subvol create /bkp/backup-subvol > cp -prv --reflink=always /bkp/backup/* /bkp/backup-subvol/ Yeah that will take a lot of writes that are not necessary, now that you see backup is a subvolume already. If you want a copy of it, just snapshot it. -- Chris Murphy
