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Re: On persistency in newer live-boot

04/09/2012 06:39 PM, anonym:
> 04/09/2012 05:11 PM, Daniel Baumann:
>> if we, as you impled, can unify the code so that snapshot and overlay
>> is being deduced by live-boot from looking at the config file, then,
>> we could use one label only.
> It ought to be pretty simple since the home-sn code practically does
> what we want already. I'll have a look at it some day soon, but I won't
> promise anything :).

I've thought some about this now, and I think the following is what
makes most sense:

Snapshots can no longer be partitions; only snapshot files are
supported. I think this is unavoidable given our wishes and constraints:

1. Since we want to use only one label for both snapshots and overlays,
   there's really no good way to distinguish between snapshot partitions
   and overlay partitions.

2. Since we want (or at least I think it'd be nice and consistent) to
   control snapshots through the live-persistence.conf file we cannot
   deal with things other than files on the same fs as the conf file.

3. Storing the live-persistence.conf file *inside* a snapshot
   partition is confusing (most options doesn't make sense any more, so
   the file now depends on the context, not only its contents), but
   there is no other place it can be stored.

If this is acceptable I propose that snapshots are activated by a
live-persistence.conf option called "snapshot=PATH_TO_SNAPSHOT_FILE"
(extension is optional). A complete example line is:

    /home snapshot=home-sn.squashfs

which is equivalent to having home-sn.squashfs on some random fs in
current live-boot.

We could probably drop support for /etc/live-persistence.binds
(currently only available by cpio snapshots) since the same result is
achievable by creating one snapshot per directory we otherwise would
list in the .binds file. I suppose we could allow several
directories/lines to use the same snapshot file too, e.g.:

    /home snapshot=example.ext2
    /etc  snapshot=example.ext2

which would give the exact same functionality (since the /etc and /home
are stored in the exact same snapshot file now, not separate ones), but
I suspect that may be a bit tricky to implement since all those lines
can't be treated individually.



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