On 05/13/2014 10:09 AM, Colin Walters wrote:
If I can put /usr on a different subvolume which will include
/usr/bin, /usr/sbin, /usr/lib, and /usr/lib64, then I should be able
to put /etc on a separate subvolume and anaconda should be enhanced
to permit it.
That gets really messy though, because /etc/fstab is what contains the
partition configuration...
When I realized how well this worked and how easy it was to do, I
wanted to do the same thing for /etc becuase I change a lot of stuff
in it such as /etc/libvirt definitions.
Right, the tricky thing with /etc is that it is a mix of OS defaults
and your custom state. That's why the OSTree model introduces
/usr/etc which holds defaults; so at any point, you can do "ostree
admin config-diff" and get a diff of just your changes to /etc. You
can then just back this up.
The reason OSTree needs /usr/etc is to implement upgrades - it ensures
your changes propagate forwards.
The "OSTree" is new to me. I have not seen it previously mentioned.
Also, /usr/etc ? Is this something new in Fedora 21?
OK, is putting /usr on a different btrfs subvol a bug or a feature?
I'd say it's an option. You can snapshot /usr and that's OK but it
does lead to questions about /etc and the other major directories:
/boot and /var. Basically if you use snapshots of /usr you get to keep
both pieces (literally! ;) )
Doing snapshots is only part of the solution. Then it is using
btrfs-send to put baseline and delta files on some backup system. If
your system goes tango-uniform then you can restore much easier with
those backups. With respect to the backup of /etc, for restore I would
bring back the shapshots and then selectively copy my updates from the
snapshot to the new /etc. I always assume that I will be re-installing
the system so that it is my data and configuration changes I need to use
for the re-installed system.
/boot on a btrfs subvol is interesting. I seem to remember cmurph
mumbling something about wanting to boot off snapshots ... you know,
that just might work! I think I will give it a try.
BTW, how about re-enabling btrfs subvols, btrfs volumes, and LVMlv in
anaconda? With the updated grub2-2.02 and os-prober in rawhide, all you
need is my grubby.c patch and, like magic, it works the way it is
suppose to.
Gene
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