Re: [RFC/dpkg PATCH] Introducing an relaxed-Essential-like "Important" field
On Wed, Mar 09, 2016 at 05:36:56PM +0000, Ian Jackson wrote:
> Julian Andres Klode writes ("Re: [RFC/dpkg PATCH] Introducing an relaxed-Essential-like "Important" field"):
> > Are there any better proposals?
>
> Do we want this field to be ignored by old versions of the tools, or
> to prevent installation of the package ? I think the answer is (a) in
> which case we probalby need a new field.
>
> If the answer were (b) we could use `Essential: sort-of' or something.
Definitely (a). Most software does not need to know about the field.
What options are there:
1. Important synonyms:
Significant: yes
Crucial: yes
Vital: yes
2. Removal-related:
Removable: no (or Removable: force)
Do-Not-Remove: yes
Discourages-Removal: yes
3. others
Keep: yes
>
> I agree with the qualms about `important'.
>
> Also we need to consider how to allow the user to switch between
> different programs which have this flag set. There needs to be a
> user-friendly flag on apt, I think. (Maybe there already is.)
I'd believe that a Replaces/Breaks or Replaces/Conflicts from one
package to another providing the same feature set would be the
way to go.
>
> Perhaps the control field name should follow the UI decision.
I don't really know. Maybe "Removal of this package is
discouraged", thus something like:
Discourages-Removal: yes
I think that's clear to anyone. But maybe it's too clear as
it basically restricts it to removal only.
Other things APT does with the field:
1. APT assigns "Important" packages a higher score than other
packages in the solver (the solver treats Important as Essential)
2. APT treats Important packages like Essential when Breaking a
loop with an early removal to prevent a temporary removal of
it
You could say that both actually contribute to the goal of
preventing the removal, but (1) probably seems like a semantic not fit
for a field named like that.
Basically, we just dropped the immediate configuration part
APT does for essentials (apt-pkg/packagemanager.cc),
the automatically installing of new essential packages
(apt-pkg/upgrade.cc), and they do not get an extra score
in the ordering algorithm (apt-pkg/orderlist.cc).
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