How to obtain list of installed packages

[Ralf Mardorf]

On Fri, 20 May 2016 16:27:16 +0800, Bret Busby wrote:
>the HDD has the partitions that existed when the system was purchased
>(about four or five, I believe)

They are unlikely Linux journaling file systems. This shouldn't be
related to a warning or error, but it might be better to use Linux file
systems.

>If I knew how to reproduce the particular error message, it would
>probably be quite helpful, in all of this, as I may be completely
>wrong, in my perception of the need to rebuild the file systems on the
>HDD.

When did you see the error message? By startup messages? When running a
program?

What do you get when running on or all of the below programs?
  sudo parted -l
  sudo fdisk -l
  sudo gparted

Take a look at
  man fsck
or perhaps it's easier to read 
https://help.ubuntu.com/community/FilesystemTroubleshooting
I didn't read the help, but I noticed that "touch /forcefsck" perhaps
should be run as "sudo touch /forcefsck".

Regards,
Ralf