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
