On Tue, Apr 7, 2015 at 6:40 PM, Hugo Mills <h...@carfax.org.uk> wrote: > On Tue, Apr 07, 2015 at 06:31:36PM +0200, arnaud gaboury wrote: >> On Tue, Apr 7, 2015 at 4:20 PM, Hugo Mills <h...@carfax.org.uk> wrote: >> > On Tue, Apr 07, 2015 at 01:08:59PM +0200, arnaud gaboury wrote: >> >> On Tue, Apr 7, 2015 at 1:03 PM, Hugo Mills <h...@carfax.org.uk> wrote: >> >> > On Tue, Apr 07, 2015 at 12:58:28PM +0200, arnaud gaboury wrote: >> > [snip] >> >> >> After more reading, it seems to me creating a top root subvolume is >> >> >> the right thing to do: >> >> >> # btrfs subvolume create root >> >> >> # btrfs subvolume create root/var >> >> >> # btrfs subvolume create root/home >> >> >> >> >> >> Am I right? >> >> > >> >> > Not how I'd recommend doing it. I'd say: >> >> > >> >> > # btrfs sub crea root >> >> > # btrfs sub crea var >> >> > # btrfs sub crea home >> >> > >> >> > Then fstab: >> >> > >> >> > LABEL=myfs / btrfs subvol=root 0 0 >> >> > LABEL=myfs /var btrfs subvol=var 0 0 >> >> > LABEL=myfs /home btrfs subvol=home 0 0 >> >> > >> >> > And finally, add this to your kernel command line in the bootloader >> >> > to specify how to mount root: >> >> > >> >> > rootflags=subvol=root >> >> > >> >> > Hugo. >> >> >> >> Thank you Hugo. May you please tell why your recommendation is better >> >> than my settings, if I thereafter make root as the default sub-volume? >> >> I changed the root name to active and avoid any confusion: >> > >> > Well, keeping the subvolumes separate from each other, rather than >> > nested, makes it a bit easier to do things like replace one subvolume >> > with an earlier snapshot. If you nest them, then your recovery process >> > from (say) a screwed-up / looks a bit like this: >> > >> > # mount -o subvolid=0 /dev/sda1 /media/btrfs >> > # mv /media/btrfs/root /media/btrfs/old-root >> > # btrfs sub snap /media/btrfs/old-root/snapshots/last-root >> > /media/btrfs/root >> > # btrfs sub snap /media/btrfs/old-root/var /media/btrfs/root/var >> > # btrfs sub snap /media/btrfs/old-root/home /media/btrfs/root/home >> > # btrfs sub set-default $n /media/btrfs >> > # umount /media/btrfs >> > >> > If you don't nest them, and don't use set-default, then the same >> > recovery process would look like this: >> > >> > # mount -o subvolid=0 /dev/sda1 /media/btrfs >> > # mv /media/btrfs/root /media/btrfs/old-root >> > # mv /media/btrfs/snapshots/last-root /media/btrfs/root >> > # umount /media/btrfs >> > >> > (This also explains why I wouldn't use set-default, but instead >> > mount / using a subvol=<path> option). >> > >> > Now, for making the snapshots in the first place, with nested >> > subvolumes, your snapshot script looks a bit like this: >> > >> > # btrfs sub snap / /snapshots/last-root >> > >> > and with the approach I'd recommend, it looks like this: >> > >> > # mount -o subvolid=0 /dev/sda1 /media/btrfs >> > # btrfs sub snap /media/btrfs/root /media/btrfs/snapshots/last-root >> > # umount /media/btrfs >> > >> > which is a little more complex, but the approach is precisely similar >> > to the recovery process: mount the top level of the FS on >> > /media/btrfs, manipulate the subvolumes, and then unmount. This keeps >> > the management of subvolumes a completely separate concern from the >> > structure of the filesystem tree. >> > >> > Hugo. >> >> Thank you for all these info. >> Here is my setup now. I hope I fully understand all the hints. >> >> $ cd /mnt/btrfs >> # btrfs subvolume create active ---> Just in case I want to add >> another subvolumes >> # btrfs subvolume create active/rootvol >> # btrfs subvolume create active/home >> # btrfs subvolume create active/var >> # btrfs subvolume create active/etc > > One minor thing -- you've still got nested subvolumes here. You can > still run into the same kinds of management problems (not being able > to use mv efficiently to move subvolumes around). "active" doesn't > need to be a subvolume, it can (and, I'd argue, should) be an ordinary > directory. > > Hugo.
So in mnt/btrfs, # btrfs subvolume delete ... deleted all subvolumes. Checked list was empty. Then: $ cd /mnt/btrfs # btrfs subvolume create rootvol # btrfs subvolume create home # btrfs subvolume create var # btrfs subvolume create etc Basic and no nested volumes. No default subvolume. Is this finally correct? Thank you > > -- > Hugo Mills | What do you give the man who has everything? > hugo@... carfax.org.uk | Penicillin is a good start... > http://carfax.org.uk/ | > PGP: E2AB1DE4 | -- google.com/+arnaudgabourygabx -- 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
