Re: Several questions regarding btrfs

[Andrei Borzenkov <arvidjaar@gmail.com>]

01.11.2017 15:01, Austin S. Hemmelgarn пишет:
...
> The default subvolume is what gets mounted if you don't specify a
> subvolume to mount.  On a newly created filesystem, it's subvolume ID 5,
> which is the top-level of the filesystem itself.  Debian does not
> specify a subvo9lume in /etc/fstab during the installation, so setting
> the default subvolume will control what gets mounted.  If you were to
> add a 'subvolume=' or 'subvolid=' mount option to /etc/fstab for that
> filesystem, that would override the default subvolume.
> 
> The reason I say to set the default subvolume instead of editing
> /etc/fstab is a pretty simple one though.  If you edit /etc/fstab and
> don't set the default subvolume, you will need to mess around with the
> bootloader configuration (and possibly rebuild the initramfs) to make
> the system bootable again, whereas by setting the default subvolume, the
> system will just boot as-is without needing any other configuration
> changes.

That breaks as soon as you have nested subvolumes that are not
explicitly mounted because they are lost in new snapshot.