Re: btrfs problems and fedora 14
Thank you all for your help and in particular you cwillu (sounds strangely formal!). Yes, I can now boot into a snapshot but I thought it might be helpful to explain why I thought otherwise. I am totally anal about having backups of a current operating systems and using those for testing I thought tat the best way to do this with btrfs was to rsync the file system to another partition but exclude all snapshots. This worked very well as long as I mounted only the root file system of the copy but what I did was add snapshots to the copy and at some point (probably at the start) the btree system was corrupted but I only saw this on backtracking and checking all messages. Also, I didn't want to boot from a snapshot of my working operating system for fear I could screw things up and have to re-install from scratch. In order to try again, I deleted all snapshots from the original system, did an rsync and checked the copy. I then made a snapshot of the copy via yum, used rootflags and it worked!! So, cwillu, after your scolding of me and your (perfectly reasonable) questioning of my understanding, I did get it together for booting. BUT I am still left with the problem that caused it for me: how do I backup (clone?) a btrfs file system with snapshots to another btrfs partition (apart from using dd). I just hope I don't get scolded again and told I am not up to it. On Wed, 2010-11-24 at 03:19 -0600, cwillu wrote: On Wed, Nov 24, 2010 at 1:32 AM, david grant d...@david-grant.com wrote: Hugo, you told me how to mount a snapshot. Thank you, that works but you didn't tell me how to boot into it. He also gave you the command to set the default subvolume/snapshot used if you don't provide one: btrfs subvolume set-default id path. There's also a standard way to send mount options for the root filesystem, which would allow you to use the mount options he provided (which Anthony pointed out in his email). Anthony, I really hoped that you had provided the answer using grub but all combinations of your suggestions result in a boot failure with standard error message of unable to mount root because of of wrong fs type etc. I assume that with your suggestion I need a standard fstab entry with default options but it doesn't work even with subvol options. I am always nervous of messing with the MBR so I want to stick with grub. He meant that you distribution uses an initial ram filesystem loaded into memory with necessary modules, placed in the same place as the kernel image that grub loads. This is unrelated to the MBR. Perhaps this is a fedora problem but I have to say I find it very strange that they tout btrfs as the future, particularly with respect to rollbacks but provide no guide to doing this. I assume it is a combination of grub boot parameters and fstab but nobody seems to know what to do. The future != the present. Btrfs will make things like rollback easy to implement, but it's not implemented yet in useful way for an untechnical user. The hard technical bits are over and done with by the time there are guides on the various forums about how to do rollback with btrfs. I am not a techo so I just need simple instructions. Is there any other site, I should be posting this on? Not to belabour the point, but a more careful reading of what people told you would have gotten you up and running. If those instructions were too technical, then you probably shouldn't be using btrfs yet: it's very much at a some assembly required stage, and if you don't understand how your system boots at a basic-but-technical level, you're either going to come away frustrated, or you're going to have to learn at least some linux administrator 101. :) Understand what the commands people are giving you actually do, and you'll have this working in no time. [sorry for sending this twice David, I consistently fail to hit reply to all when replying to mailing lists] :( -- 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
Re: btrfs problems and fedora 14
Thank you all for your responses to my boot snapshot problem but it still exists. . Hugo, you told me how to mount a snapshot. Thank you, that works but you didn't tell me how to boot into it. Anthony, I really hoped that you had provided the answer using grub but all combinations of your suggestions result in a boot failure with standard error message of unable to mount root because of of wrong fs type etc. I assume that with your suggestion I need a standard fstab entry with default options but it doesn't work even with subvol options. I am always nervous of messing with the MBR so I want to stick with grub. Perhaps this is a fedora problem but I have to say I find it very strange that they tout btrfs as the future, particularly with respect to rollbacks but provide no guide to doing this. I assume it is a combination of grub boot parameters and fstab but nobody seems to know what to do. I am not a techo so I just need simple instructions. Is there any other site, I should be posting this on? Thanks in anticipation On Tue, 2010-11-23 at 00:45 -0600, C Anthony Risinger wrote: On Mon, Nov 22, 2010 at 10:47 PM, Wenyi Liu qingshen...@gmail.com wrote: 2010/11/23, david grant d...@david-grant.com: I thought I would try btrfs on a new installation of f14. yes, I know its experimental but stable so it seemed to be a good time to try it. I am not sure if I have missed something out of all my searching but am I correct in thinking that currently: I. it is not possible to boot from a snapshot of the operating system and, in particular, the yum snapshots cannot be used for that purpose Is the Fedora grub support btrfs now? In this page http://fedoraproject.org/wiki/Features/SystemRollbackWithBtrfs I got the following information: (deferred) a patch to grub1 -- on top of the already existing patch to support btrfs in grub1 -- to allow selecting between snapshots of the boot partition. all you need to do is add: subvol=name of the snapshot -- or -- subvolid=id of the snapshot to your kernel boot line (edit in grub on the fly)... however, if fedora is like archlinux in this respect (brief google search seems to agree), you will actually need to add this: rootflags=subvol=name of the snapshot where `rootflags` are the mount options passed to the initramfs/root device. also, you rally don't need grub, whatsoever[1]; in arch, we use an initramfs hook to perform system rollback by dynamically modifying the rootflags in accordance with the user's choice: http://aur.archlinux.org/packages/mkinitcpio-btrfs/mkinitcpio-btrfs/btrfs_hook perhaps someone in fedora can adapt that script... it's rather simple, and it's MUCH easier and safer than fiddling with grub legacy[1]. C Anthony [1] note however, that a proper grub2/extlinux solution is ideal to support kernel-level rollbacks. in the link above, everything is rolled back except the kernel (residing on /boot... non-btrfs). though, a kexec solution may be possible. -- 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
btrfs problems and fedora 14
I thought I would try btrfs on a new installation of f14. yes, I know its experimental but stable so it seemed to be a good time to try it. I am not sure if I have missed something out of all my searching but am I correct in thinking that currently: I. it is not possible to boot from a snapshot of the operating system and, in particular, the yum snapshots cannot be used for that purpose II. it is so easy to create raid arrays of btrfs partitions but they cannot be read by f13 or f14 III. it is not possible to copy btrfs partitions with snapshots except possibly by the use of dd. This is not meant to be a put down of btrfs but a plea to have some clarification and in particular the ability to boot snapshots. Hope I can get a response -- 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
