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DESIGN: More explanation of problem

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Initial thoughts on booting details.
This commit is contained in:
Colin Walters 2011-10-09 18:52:26 -04:00
parent 878b53c626
commit 5a59c29371
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DESIGN
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@ -7,6 +7,56 @@ manages root filesystems. They both share an executable name
hacktree-build hacktree-build
hacktree-root-manager hacktree-root-manager
== Problem statement ==
Hacking on the core operating system is painful. We want a system
that matches these requirements:
0) Does not disturb your existing OS
1) Is not terribly slow to use
2) Shares your $HOME - you have your data
3) Allows easy rollback
4) Ideally allows access to existing apps
== Comparison with existing tools ==
Virtualization:
Fails on points 1) and 2).
Rebuilding OS packages:
Fails on points 0) and 3). Is also just very annoying.
jhbuild + OS packages:
The state of the art in GNOME - but can only build non-root things -
this means you can't build NetworkManager, and thus are permanently
stuck on whatever the distro provides.
== The core idea ==
chroots are the original lightweight "virtualization". Let's use
them. So basically, you install a mainstream distribution (say
Debian). It has a root filesystem with a regular layout, /etc, /usr,
/lib etc.
Now, what we can do is have a system that installs chroots, like:
/gnomeos/root-3.0-opt
/gnomeos/root-3.2-opt
These live in the same root filesystem as your regular distribution
(Note though, the root partition should be reasonably sized, or
hopefully you've used just one big partition).
We allow booting into these roots via a modified dracut - if you have
this system installed, at boot time it shows a prompt like:
[0] Default root
[1] /gnomeos/root-3.0-opt
[2] /gnomeos/root-3.2-opt
If you pick [1] or [2], then instead of calling switch_root for /,
it uses the selected root.
== The recipe set == == The recipe set ==
A recipe is similar to Bitbake's format, except just have metadata - A recipe is similar to Bitbake's format, except just have metadata -
@ -116,6 +166,8 @@ we then diff?
If the script fails, we can roll back the update, or drop to a shell If the script fails, we can roll back the update, or drop to a shell
if interactive. if interactive.
== Booting ==
== Local modifications == == Local modifications ==
A key point of this whole endeavour is that we want developers to be A key point of this whole endeavour is that we want developers to be