[Fedora-livecd-list] [PATCH] persistence - VERY ROUGH first pass

[Jeremy Katz]

On Tue, 2007-07-24 at 03:43 -0500, Douglas McClendon wrote:
> Attached is a _first pass_ patch that enables LiveOS persistence for 
> livecd-tools.  Before you read this and get _too_ excited, note that I'm really 
> only posting this because of the f8t1 devel freeze.  If I get any encouragement, 
> I am very willing to work my ass off in the next few days to get this cleaned up 
> into respectable shape for a potential f8t1 feature.  But I also realize it is 
> probably just too late for that. (OTOH the code is already structured so that it 
> is obvious that in the absence of a persistence bootarg, the code has no impact)

Given where a few things stand[1], I'd prefer to hold off until
post-test1.  Although this definitely looks like a good start

> The Principals Of OPeration are-
> 
> - unless a boot argument of "persistence[=[devspec][:pathspec]]" is seen, 
> nothing will behave differently, except for the existence of a new tool 
> /usr/sbin/livetool

Sounds good for now; we'll almost certainly want to make it default to
automatic eventually with the option being to not do it.  

> - after booting normally (no persistence bootarg), if you invoke

As long as nothing has been found, it should be fine to do this, no?
Also, instead of using the label as the key, we might want to go for
something better and UUID based.  I'm just a little worried that labels
aren't unique enough.  

> - devspec can be in the following forms (should be obvious what they mean),
> and defaults to auto, which means to search all mountable partitions.  (the 
> search process mounts readonly (with paranoid blockdev --setro as well)

blockdev --setro is an awesome idea.  Having to use fuse for ntfs is
annoying at best, fragile if we go further.  How much is it really worth
to be able to have it on ntfs?

> - pathspec defaults to /LiveOS/Persistence-LIVEOS_LABEL
> (e.g. /LiveOS/Persistence-Fedora-7-Live-i386)
>
> if pathspec does not start with a /, it prepends the above default.
> (e.g. persistence=:dmc would mean to search all partitions for 
> /LiveOS/Persistence-Fedora-7-Live-i386-dmc)

Per above, I think that we want to have it tied to the UUID of the live
image.  At which point, specifying it becomes more for
 * Putting it buried somewhere on the filesystem other than /LiveOS
 * Handling multiple persistence on the same media
The first I can sort of see... the second seems like it's probably less
useful.  Especially once the label isn't the important part

> Finally: Known bugs:
> 
> 1) I had to comment out the mayflower generated init's trap and set -e

It might be worth integrating directly into the mayflower init.  I'm not
opposed to keeping it separate, though.  Keeping it separate might
actually help a little as I try to spend some time to get us to a more
stock initramfs

> 2) ext3's inability to mounted readonly is annoying (yeah, I know norecovery or 
> ext2 will probably get it for me, still annoying)

Yeah -- what happens when you try to mount it with the block device
read-only and a dirty journal?

> 3) choice handling is broken.  Don't use auto when it will find more than one 
> entry.  Maybe just don't use auto at all.

We definitely want auto.  With more than one entry, maybe we should just
bail?  Asking for input is bound to be tricky given things like USB
keyboards

> Well, that about covers it for now.  As always, comments, suggestions, and 
> criticisms will be greatly appreciated.  (though feel free to wait 48 hours for 
> plenty of obvious improvements, such as fixing those known bugs).
> 
> "release early, release often"...

Thanks for getting a good start on this!

Jeremy

[1] Having to fight entirely unrelated things to get working images spit
out just due to distro flux