George Mitchell posted on Sun, 03 Aug 2014 21:00:19 -0700 as excerpted: >>> I cannot mount my root with anything other than an explicit /dev/sdx >>> reference until I manually run a scan. Then UUID etc all work. I've >> That sounds like a problem with the Ubuntu initrd, probably filing an >> Ubuntu bug report would be the best thing to do. Is BTRFS supported in >> that version of Ubuntu? >> >> But just changing your boot configuration to use /dev/sdx is probably >> the best option. >> > Assuming you are booting with grub2, you will need to use /dev/sdx in > the grub2 configuration file. This is known issue with grub2. Example > from my script: > > ------------------------------------------------------------------------ > echo 'Loading Linux desktop ...' > linux /vmlinuz-desktop root=/dev/sda7 ro splash quiet > echo 'Loading initial ramdisk ...' > initrd /initrd-desktop.img > > ------------------------------------------------------------------------
?? Known issue with ubuntu's grub2, perhaps? Or perhaps with separate initrds as opposed to kernel-appended initramfss? Or maybe it's with loadable kernel modules as opposed to a custom-built monolithic kernel? Or maybe it's an issue with mbr style grub2 but not gpt with a dedicated BIOS boot partition, or perhaps with grub2 in EFI mode instead of BIOS mode? Because it works just fine here, grub2, root=LABEL= style root= line pointed at a multi-device btrfs rootfs, BIOS mode gpt partitions with a dedicated BIOS partition for grub2 to use, custom built monolithic kernel with all necessary modules builtin and an appended initramfs, not a separately loaded initrd. As rootfs /is/ a multi-device btrfs I /do/ have to have an initramfs, because apparently the kernel's command-line parser doesn't properly handle the btrs device= mount option in rootflags=device= parameters, and without a userspace btrfs device scan, the btrfs device= mount option must be passed for multi-device filesystems or btrfs will refuse to mount the device without degraded. But with an appropriate initramfs, it most certainly does work here. FWIW, my initramfs is dracut-based, btrfs and udev dracut modules loaded of course, with or without the systemd dracut module also loaded (I recently converted to systemd and was running the non-systemd dracut before that. And root=LABEL= works just fine. In fact, I have grub2 variables setup with the labels for several different rootfs choices, working multi-device btrfs rootfs, primary backup multi-device btrfs rootfs, and secondary backup reiserfs rootfs. I then have a grub2 menu setup that lets me choose between the three, substituting in the appropriate grub2 variable based root=LABEL= kernel commandline option as necessary. With the previously mentioned exception of having to use the initramfs in the first place in ordered to work around the kernel's rootflags=device= parsing issue instead of being able to direct-boot the rootfs without an initramfs at all, it all works exactly as expected. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- 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
