On Mon, Jan 10, 2011 at 09:22:49AM +0700, Fajar A. Nugraha wrote: > On Mon, Jan 10, 2011 at 5:01 AM, Hugo Mills <hugo-l...@carfax.org.uk> wrote: > > There is a root subvolume namespace (subvolid=0), which may contain > > files, directories, and other subvolumes. This root subvolume is what > > you see when you mount a newly-created btrfs filesystem. > > Is there a detailed explanation in the wiki about subvolid=0? What > does "top level 5" in the output of "btrfs subvolume list" mean (I > thought "5" was subvolid for root subvolume)? > > # btrfs subvolume list / > ID 256 top level 5 path maverick-base > ID 257 top level 5 path kernel-2.6.37 > > > The default subvolume is simply what you get when you mount the > > filesystem without a subvol or subvolid parameter to mount. Initially, > > the default subvolume is set to be the root subvolume. If another > > subvolume is set to be the default, then the root subvolume can only > > be mounted with the subvolid=0 mount option. > > ... and mounting with either subvolid=5 and subvolid=0 gives the same > result in my case.
OK, having read through some of the code, it looks like the "5" comes from it being the root FS tree object ID. So, it's probably quite hard to change that number without making incompatible filesystems. However, the _documented_ (and official) way to mount the root subvolume is to use subvolid=0... :) Hugo. -- === Hugo Mills: h...@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- But people have always eaten people, / what else is there to --- eat? / If the Juju had meant us not to eat people / he wouldn't have made us of meat.
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