How to obtain list of installed packages

[Tom H]

On Wed, May 11, 2016 at 2:05 PM, Bret Busby <bret.busby at gmail.com> wrote:
> On 11/05/2016, Tom H <tomh0665 at gmail.com> wrote:
>> On Wed, May 11, 2016 at 12:47 PM, Ralf Mardorf <silver.bullet at zoho.com>
>> wrote:
>>> On Wed, 11 May 2016 12:06:29 +0200, Tom H wrote:
>>>>
>>>> The best answer's the one that proposed an aptitude search because it
>>>> returned the list of packages that were installed specifically rather
>>>> than automatically.
>>>
>>> this isn't a good advice.
>>>
>>> A pitfall could be that some packages are installed with the
>>> recommended packages, but others were not installed with recommended
>>> packages. This is important even when installing the same Ubuntu
>>> release and fails when following your advice Tom.
>>
>> Not at all.
>>
>> You can run "aptitude -F %p search '?narrow(?installed,!?automatic)'"
>> (or "aptitude -F %p search '~S ~i !~M'") to get the list of packages
>> that were installed manually.
>
> Ah, no.
>
> Because, after I installed aptitude (it was not installed, when I
> first tried to run the command), and, again ran that command, as
> shown, it listed all kinds of packages that I had no knowledge of
> installing.

Don't be ridiculous!

Did you install "apt"? Isn't it installed?

How about "acl", "adduser", "anacron", "apparmor", "apport", ...? (And
these are the As that I can remember off-hand.)