"My bug" is related to that one, so I am adding the information as comment rather than creating a new one. However, if you think it is "enough different" let me know and I will create a separate bug.
I wanted to install Ubuntu Server on a system with 3 disks using Btrfs in RAID5. My first attempt was with Ubuntu 12.04.4 LTS but the btrfs tools shipped with it do not support RAID5. So I decided to go with Ubuntu Trusty Thar Alpha 2 (build from the 2014-02-08) and try my luck with it. This release of Ubuntu Server supports Btrfs in RAID5 although the installer does not. So during the "partitionning" phase I switched to another terminal to create the Btrfs filesystem in RAID5. All was set-up correctly and the rest of the installation process was successfully done (in the log and as far as I can tell on the FS itself, all required files and configuration have been created). The problem is that the step to install Grub failed miserably with the same error as reported initially in this bug report. I can provide some insight why this fails. Lines 295-314 from grub- installer (not grub-install, but the one used during installation). This script tries to find the root and boot mount point and the filesystem type of /boot. The problem of the functions findfs and findfstype in the case of RAID (in redundant mode, so RAID1,5,6,10 at least for Btrfs) is that they will find on all my 3 devices (sda, sdb and sdc) a /boot partition! So when a few lines later the script calls mapdevfs and use the $rootfs and $bootfs parameters, instead of showing /dev/sda2 (in my case) it has /dev/sda2 /dev/sdb2 /dev/sdc3, and obviously mapdevfs complains to support the 3 devices given as parameters. When debuging the script grub-installer (using the "set +x" option), I have found out that the following command returns: # chroot /target grub-probe -t device /boot /dev/sda2 /dev/sdb2 /dev/sdc2 Which is then not foreseen for the rest of the scripts. I wrote an ugly patch which works for me, I changed the lines 295-296 to rootfs=$(findfs / | head -n1) bootfs=$(findfs /boot | head -n1) I then ran the following command: grub-installer /target/ /dev/sda So given the current script, it is not possible to install Ubuntu with a /boot partition using Btrfs configured with a redundant "RAID"disk (aka as of today RAID1,5,6,10). Note: this was only tested with RAID5, but obviously the other RAID configuration will be affected the same. Note: However, the script was too complex to be read in a text console to be able to correct it so that I could install on each HDD grub. Because now only /dev/sda has grub, but if it fails my system is unable to boot in degraded mode because I do not have a bootloader on sdb or sdc. I was thinking that grub-installer second parameter was the destination device. But when trying to patch the rootfs and bootfs to get sdb2, and use sdb instead of sda for grub-installer, I saw in the log that it still installed Grub in sda :-( -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1265402 Title: Unity calls mapdevfs with wrong number of args on btrfs raid1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1265402/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
