On 04.04.2026 23:37, Marvin Renich via Postfix-users wrote:
* Greg Klanderman via Postfix-users <[email protected]> [260404 15:06]:
Hi Marvin,
Thank you for your reply.. that matches what I see.
I had not realized recommends were installed by default.. I was
wondering how those and suggests differed but hadn't gotten to looking
it up yet.
I had not used --no-install-recommends, simply 'apt install postfix'
and libsasl2-modules was not installed.
[snip]
The following day, it shows that I ran 'apt upgrade' and libsasl2-2
was upgraded, but not libsasl2-modules (which appears to have matching
versioning).
I have to conclude that libsasl2-2 must have already been installed,
without libsasl2-modules, when I installed postfix.
Does that make sense? Since it was not installing libsasl2-2, the
recommends: libsasl2-modules was not considered, only the postfix
package suggests: libsasl2-modules.
Exactly.
Actually, when apt installs something new, it considers Recommends: for
*all* packages it installs. So if A depends on B, and B recommends C,
and you install A, C will be installed too (unless you disable
installing recommends). Ditto for the case when A *recommends* B, etc.
In short, by default apt installs Recommends for everything it installs.
This is why this problem hasn't been a problem for all these years.
And yes, this does not answer the question why the OP doesn't have
libsasl2-modules installed on the system. I can't answer it either.
Maybe it would make sense for postfix to directly recommend: rather
than suggest: libsasl2-modules?
I don't think so, but I'm not sure. The Debian maintainer would be the
person to decide this.
It should not. There are multiple possible sasl implementations (there's
also dovecot for example), and actually, there are a lot of installs
where nothing else besides basic mail system is needed - consider a
case of a server in a server room, which should collect mails from
cron and send it to a dedicated mailhub: such case is actually very
common. So actually we have another problem, where an *extra*,
unwanted, software is installed by default.
Choosing defaults is not a fun problem, - you cant suit every needs
out there. But I really like the way debian does here, allowing to
install a minimal system with just a bare minimum software for the
task at hand, instead of always insisting on everything being installed.
Thanks,
/mjt
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