How to obtain list of installed packages

[Colin Law]

On 10 May 2016 at 19:16, Bret Busby <bret.busby at gmail.com> wrote:
> Hello.
>
> I believe that this question gets asked from time to time, but I do
> not know that a solution has been found.
>
> The question is this; does a utility exist, that can be ran, to
> produce a list of installed packages, in a way that can be used by a
> user (system administrator), to perform a system rebuild, so as to,
> after installing the system again, ensure that all of the optional
> packages that were previously installed, are again installed in the
> new system installation?
>
> I am running UbuntuMate 15.10, on a system with other Linux operating
> system versions (which are inappropriate for the hardware), that are
> not used, installed, and, with wanting to eliminate them, and,
> repartition the HDD, for a number of reasons, including occasionally
> seeing an error message that states that the partitioning is out of
> alignment, or something (I am not sure of the exact message, or, how
> to reproduce the error message), I believe that a new installation of
> the operating system, is needed, but, I want to again, have all of the
> existing installed optional packages, installed and operable.

You could use gparted to remove unwanted partitions and resize the one
you want to keep (booting off a live image).  You might then have to
re-install grub to stop it being confused by the missing partitions.
Much less work than re-installing.  Obviously have everything backed
up first in case it goes horribly wrong.

Colin

>
> So, I figure that, if a utility exists, that can produce a list of the
> installed optional packages, that could help me to reproduce the
> system, with its current functionality, in terms of the currently
> installed, optional packages.
>
> Thank you in anticipation.
>
> --
>
> Bret Busby
> Armadale
> West Australia
>
> ..............
>
> "So once you do know what the question actually is,
>  you'll know what the answer means."
> - Deep Thought,
>  Chapter 28 of Book 1 of
>  "The Hitchhiker's Guide to the Galaxy:
>  A Trilogy In Four Parts",
>  written by Douglas Adams,
>  published by Pan Books, 1992
>
> ....................................................
>
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