Dropping /usr/share/zoneinfo/posix and /usr/share/zoneinfo/right from tzdata

[Benjamin Drung]

On Tue, 2023-01-10 at 11:49 -0800, Steve Langasek wrote:
> On Mon, Jan 09, 2023 at 07:01:05PM +0100, Benjamin Drung wrote:
> > Hi everyone,
> 
> > The tzdata package ships /usr/share/zoneinfo/posix/ (for Coordinated
> > Universal Time) and /usr/share/zoneinfo/right/ (for International Atomic
> > Time). The files in /usr/share/zoneinfo/posix/ are identical to their
> > counterpart in /usr/share/zoneinfo/. The tzdata package converts the
> > configured posix/* and right/* timezones to their unprefixed variant on
> > every package upgrade (e.g. it changes "posix/Europe/Berlin" to
> > "Europe/Berlin").
> 
> > Is there anybody actually using /usr/share/zoneinfo/posix or
> > /usr/share/zoneinfo/right?
> 
> > Aurelien and I assume that probably nobody is using them. We plan to
> > drop both directories. If nobody speaks up, I will remove them in the
> > coming weeks from the Ubuntu tzdata package prior to the feature freeze.
> > After the Debian 12 "bookworm" release, we will remove it from Debian.
> 
> In addition to fixing (or at least conflicting with) the bits identified via
> a code search (thanks, Shengjing!), I want to assert that the upgrade should
> take care of any references to these obsoleted compat links in /etc/timezone
> or /etc/localtime.  Even if the debconf automation never presented these as
> options to the user, we shouldn't break the default system timezone on
> upgrade.

Upgrading tzdata will replace the right/* and posix/* timezones.
Example: Configure tzdata 2022g-2ubuntu1:

```
$ ln -sf /usr/share/zoneinfo/posix/Europe/Berlin /etc/localtime 
$ echo "posix/Europe/Berlin" > /etc/timezone 
```

Then upgrade:

```
$ apt install ./tzdata_2022g-7ubuntu1_all.deb
[...]
Current default time zone: 'Europe/Berlin'
[...]
```

There was no user interaction when updating the tzdata package. This
replacement also works when the timezone is a symlink as well (e.g.
Europe/Busingen).

-- 
Benjamin Drung
Debian & Ubuntu Developer