On Fri, Dec 22, 2017 at 14:04:43 -0700, Chris Murphy wrote: > I'm pretty sure degraded boot timeout policy is handled by dracut. The
Well, last time I've checked dracut on systemd-system couldn't even generate systemd-less image. > kernel doesn't just automatically assemble an md array as soon as it's > possible (degraded) and then switch to normal operation as other MD devices are explicitly listed in mdadm.conf (for mdadm --assemble --scan) or kernel command line or metadata of autodetected partitions (fd). > devices appear. I have no idea how LVM manages the delay policy for > multiple devices. I *guess* it's not about waiting, but simply being executed after the devices are ready. And there is a VERY long history of various init systems having problems to boot systems using multi-layer setups (LVM/MD under or above LUKS, not to mention remote ones that need networking to be set up). All of this works reasonably well under systemd - except for the btrfs that uses single device node to match entire group of devices. Which is convenient for living person (no need to switch between /dev/mdX and /dev/sdX), but impossible to guess automatically by userspace tools. There is only probe IOCTL which doesn't handle degraded mode. > I don't think the delay policy belongs in the kernel. That is exactly why the systemd waits for appropriate udev state. > It's pie in the sky, and unicorns, but it sure would be nice to have > standardization rather than everyone rolling their own solution. The There was a de facto standard I think - expose component devices or require them to be specified. Apparently no such thing in btrfs, so it must be handled in btrfs-way. Also note that MD can be assembled by kernel itself, while btrfs cannot (so initrd is required for rootfs). -- Tomasz Pala <go...@pld-linux.org> -- 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
