On Fri, Jul 8, 2016 at 11:50 PM, Chris Murphy <li...@colorremedies.com> wrote: > On Fri, Jul 8, 2016 at 3:39 PM, Chris Murphy <li...@colorremedies.com> wrote: >> On Fri, Jul 8, 2016 at 2:08 PM, Kai Herlemann <nesa...@freenet.de> wrote: >> >>> If here any developers read along: I'd like to suggest that there's >>> automatically made a subvolume "@" by default, which is set as default >>> subvolume, or a tip to the distribution, that it would made sense to do that >>> with the installation. It would protect other users against confusion and >>> work like I had it. >> >> I think that upstream won't do that or recommend it. There is already >> a subvolume created at mkfs time, that's subvolid=5 (a.k.a. 0) and it >> is set as the default subvolume. I don't see the point in having two >> of them. If you want it, make it. If your distro wants it, it should >> be done in the installer, not mkfs. >> >> Further I think it's inappropriate to take 'btrfs sub set-default' >> away from the user. That is a user owned setting. It is not OK for >> some utility to assert domain over that setting, and depend on it for >> proper booting. It makes the entire boot process undiscoverable, >> breaks self-describing boot process which are simpler to understand >> and troubleshoot, in favor of secret decoder ring booting that now >> requires even more esoteric knowledge on the part of users. So I think >> it's a bad design. >> >> Instead those utilities should employ rootflags=subvol or subvolid to >> explicitly use a particular fs tree for rootfs, rather that hide this >> fact by using subvolume set-default. > > The only distro installer I know that works this way out of the box is > Fedora/Red Hat's Anaconda. It leaves the default subvolume as 5, but > does not install the OS there. Instead each mountpoint is created as a > subvolume in that top level, and rootflags kernel parameter and fstab > are used to assemble those subvolumes per the FHS virtually. It's > completely discoverable, you can follow each step along the way, it's > not obscured. > > The additional benefit is no nested subvolumes. > > A possible improvement for those distros that will likely continue > doing things the way they are, would be if the kernel code stated what > fs tree ID was being mounted when the default subvolume is not 5, and > neither subvol nor subvolid mount options were used. *shrug*
On a running system as non-root: $ mount | grep "on / type btrfs" /dev/sda1 on / type btrfs (rw,noatime,compress=lzo,ssd,discard,space_cache,subvolid=2429,subvol=/@/latestrootfs) On an image of a disk or some separate disk with rootfs tree mounted somewhere, I agree that it might look 'hidden'; you will have to realize that the filesystem is Btrfs and that the default subvol might not be 5, but btrfs sub list / gives the answer to what more is in the pool. -- 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
