Bug#924401: #924401 base-files fails postinst when base-passwd is unpacked

[Helmut Grohne <helmut@subdivi.de>]

On Mon, Feb 22, 2021 at 07:33:10AM +0000, Tim Woodall wrote:
> A. /etc/passwd is part of base-passwd's interface and base-files is
>    right in relying on it working at all times. Then base-passwd is rc
>    buggy for violating a policy must. Fixing this violation is
>    technically impossible.
> 
> 
> I seem to have hit this same issue independently.
> 
> Could you explain why "Fixing this violation is technically impossible"

The requirement here is that base-passwd needs to work when unpacked.
The only way to make that work is making /etc/passwd a conffile. That
would technically be possible, but it would be very annoying, because
this file is different on virtually any Debian installation. So we
cannot make it a conffile in practice. The next bet would be ensuring
that base-passwd.postinst is run before other packages' postint somehow.
Such an ordering mechanism does not exist at present and it would be
prone to dependency loops.

> As far as I can see, making base-passwd not essential, only required,
> and then making passwd and base-files pre-depend on base-passwd the
> system seems to bootstrap /etc/passed and /etc/group OK.

What you write is almost certainly self-contradictory. base-files is
essential. Anything it depends on (including base-passwd in your
scenario) is pseudo-essential and thus inherits all the same
requirements except for actually being essential. You gained nothing.
And you didn't explain how you'd make base-passwd non-essential.

> That also seems to conform to the debian policy. The oddity is that
> base-files and passwd only actually need to depend on base-passwd, not
> pre-depend on it as they only use /etc/passwd and /etc/group in the
> postinst scripts but the debian policy doesn't seem to consider this
> case.

They don't have to depend on base-passwd at all, because dependencies on
essential packages should be omitted.

I suggest that you detail on the practical issue you have been hitting.
Doing so allows evaluating prospective solutions against all relevant
use cases.

Helmut