On Wed, Dec 1, 2010 at 12:48 PM, C Anthony Risinger <anthony@xxxxxxxx> wrote: > On Wed, Dec 1, 2010 at 12:36 PM, Josef Bacik <josef@xxxxxxxxxx> wrote: >> On Wed, Dec 01, 2010 at 07:33:39PM +0100, Goffredo Baroncelli wrote: >> >>> Another point that I want like to discuss is how manage the "pivoting" between >>> the subvolumes. One of the most beautiful feature of btrfs is the snapshot >>> capability. In fact it is possible to make a snapshot of the root of the >>> filesystem and to mount it in a subsequent reboot. >>> But is very complicated to manage the pivoting of a snapshot of a root >>> filesystem, because I cannot delete the "old root" due to the fact that the >>> "new root" is placed in the "old root". >>> >>> A possible solution is not to put the root of the filesystem (where are placed >>> /usr, /etc....) in the root of the btrfs filesystem; but it should be accepted >>> from the beginning the idea that the root of a filesystem should be placed in >>> a subvolume which int turn is placed in the root of a btrfs filesystem... >>> >>> I am open to other opinions. >>> >> >> Agreed, one of the things that Chris and I have discussed is the possiblity of >> just having dangling roots, since really the directories are just an easy way to >> get to the subvolumes. This would let you delete the original volume and use >> the snapshot from then on out. Something to do in the future for sure. > > i would really like to see a solution to this particular issue. i may > be missing something, but the dangling subvol roots doesn't seem to > address the management of the root volume itself. > > for example... most people will install their whole system into the > real root (id=5), but this renders the system unmanageable, because > there is no way to ever empty it without manually issuing an `rm -rf`. > > i'm having a really hard time controlling this with the initramfs hook > i provide for archlinux users. the hook requires a specific structure > "underneath" what the user perceives as /, but i can only accomplish > this for new installs -- for existing installs i can setup the proper > "subroot" structure, and snapshot their current root... but i cannot > remove the stagnant files in the real root (id=5) that well never, > ever be accessed again. > > ... or does dangling roots address this? i forgot to mention, but a quick 'n dirty solution would be to simply not enable users to do this by accident. mkfs.btrfs could create a new subvol, then mark it as default... this way the user has to manually mount with id=0, or remark 0 as the default. effectively, users would be unknowingly be installing into a subvolume, rather then the top-level root (apologies if my terminology is incorrect). C Anthony -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
