On 06/13/2012 09:21 AM, Arne Jansen wrote: > On 13.06.2012 09:04, C Anthony Risinger wrote: >> On Fri, Jun 8, 2012 at 2:40 PM, Arne Jansen <sensi...@gmx.net> wrote: >>> On 06/08/2012 09:24 PM, Matthew Hawn wrote: >>>> I just converted my root filesystem to btrfs with btrfs-convert. However, >>>> since I am running Ubuntu, I would like to have the same subvolume >>>> structure as a default install,. How do I move the top-level subvolume >>>> (where all my files currently are) to another subvolume? >>> >>> Just snapshot the root subvol and continue working in the snapshot. >> >> ... yeah but that solution totally sucks when you: >> >> a) have a lot of data >> b) need to do this via script >> c) ??? >> >> ... because in a), data will *copied* the slow way, and in b) you >> leave a bunch of junk laying around in the old root that will rot >> unless you `rm -rf` it ... and idk about you, but issuing what is very >> near to that command on someone else's machine -- via script -- makes >> me REALLY uneasy ;-) > > well, don't put data in the top level in the first place. Yes, you have > to remove the content of the subvol / by rm -rf, but I don't really see > the problem with it.
It is slow. You have to change a lot of metadata (each shared metadata block have to be unshared, and then one copy will be deleted ). > What I don't understand is why you think data will be copied. > >> >> i have asked this exact question at least 4 times specifically, and >> referenced it probably 8-10, in the last 3 years or more. i needed it >> then. i still need it now. but since i never got an answer up/down >> or around, i gave up and told people to `rm -rf`themselves ... >> >> http://markmail.org/message/7hj5ioqrztkeerqv >> >> ... that's from May of 2010, but i don't think it's the first. >> >> so, would it possible to implement this, or could someone kindly (and >> briefly!) explain why it cannot be done? > > The default subvol ('/') has the special number 5 and is expected to > always be around. All other subvols get numbers starting with 256. > Creating a new 5 and internally renumbering the old 5 isn't easy, because > each tree block has an owner recorded in it. Also, all backreferences > have the root number in them. If you have to touch each tree block, you > can as well choose the snapshot/rm -rf approach. I don't know very well the internal of btrfs. Do you think that It is possible to move/swap the root subvolume ? > >> [...] > Or you could hack mkfs.btrfs to always create an additional subvol. Which can be the default one: so nobody should complain. I > Even making / readonly except for creating mountpoint could be possible. > Just some random ideas... > > -Arne > >> > > -- > 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 > . > -- 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
