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Just a few questions about Btrfs:

  1. Do I have to mount a Btrfs filesystem before creating subvolumes on it?
  2. Can I easily convert an existing directory into a subvolume? (i.e. if I want to make "/home" a separate subvolume can I just go mk_btrfs_subfolder /home (or whatever the command is), instead of having to make a new empty subvolume and copying everything over?

The commands to do the above would be good but not necessary, just yes/no will be fine and I can Google how.

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up vote 0 down vote accepted
  1. Yes.
  2. No.

At least not at the moment.

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This answer is incomplete. Please expand. – n0pe Mar 7 '13 at 18:22
@MaxMackie I'd love to expand, but please state the question first. Do you want reference? Do you want working example of how to mount btrfs volume? Or even better: if you have more questions, post them as separate post. – Adam Ryczkowski Mar 8 '13 at 11:06

Yes you have to mount it, and if you want to convert a directory into a subvolume what you can do is create a snapshot using

btrfs su sn <name of subvolume containing folder> @new_subvol

Then you could go into the subvolume and delete everything other than @new_subvol/home for instance and move everything in home to the root of the new subvolume with something like

mv @new_subvol/home/* @new_subvol

Then you could delete the original directory and move the newly created snapshot into its place.

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The asker wants to do it "instead of having to make a new empty subvolume and copying everything over," which it seems your answer is suggesting, no? – Geremia May 27 at 17:35
Actually, your method is the proper one so as to avoid making new extents. – Geremia May 27 at 18:03
Also, couldn't you just rename home to something like home_old and then move everything from that to @new_subvol? – Geremia May 27 at 18:26

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