On Fri, Jul 8, 2016 at 11:30 PM, Andrei Borzenkov <arvidj...@gmail.com> wrote: > 09.07.2016 00:50, Chris Murphy пишет: >>> >>> 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. >> > > Does it use grub2? Where /boot/grub is located - on one of those > snapshots or on partition outside of btrfs control?
GRUB yes. The installer only permits /boot on ext4 due an ancient grubby (not GRUB) bug [1]. It's not dissimilar to openSUSE where /boot is on ext4, and Btrfs ends up on encrypted LVM, if you choose to encrypt. It's rather head shaking but that's the state of affairs. > Does it support booting from previous read-only snapshot directly and/or > rollback to previous snapshot? Not by default. Snapper is in the repos. It looks like the future of rollbacks on Fedora is to not do snapshots at all, but to deploy binaries using rpm-ostree which provides atomic OS updates on any file system. The update is only ever applied to a new tree, not the currently active tree, so if the update fails that new tree is just deleted, it's never even attempted for reboot. Some of the directories, most notably /usr, are always read-only. Basically this is a kind of stateless and therefore resettable machine. As far as I know there are no optimizations for Btrfs, where either snapshots or reflinks could be employed instead of depending on hardlinks. -- Chris Murphy -- 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
