User with uid 1001: who is this

[Tom Mitchell]

On Fri, Nov 4, 2022 at 2:23 AM Colin Law <clanlaw at gmail.com> wrote:
>
> On Fri, 4 Nov 2022 at 08:28, robert rottermann <robert at redcor.ch> wrote:
> >
> > Hi there
> >
> > I have a folder on my Ubuntu 20.04 that has owner 1001 like so:
> >
> > drwxrwxrwx  8   1001 abacus    4096 Nov  3 14:44  if_fernuni/
> >

I suspect an old adventure.
I did a google search for "abacus software ubuntu" there are many.
You can do a find with these flags:
    -uid n File's numeric user ID is less than, more than or exactly n.
    -gid n File's numeric group ID is less than, more than or exactly n.
You can save in a file or pass to xargs to see when it was created.
In this case you can do a "stat  folderUfound" and any contents.

> > now I do not find any user with id 1001.
The system would have looked up the name if there was one mapped to 1001.
Do double check both the passwd file and shadow file.
There are packages that rightly run with their own user UID and group GID.
They tend to be services or applications that aspire to update themselves or
have control of devices like printers.
A unique UID/GID allows cron jobs to clean up scratch files and rubbish
and not trespass on stuff they do not own.

It is harder to get these special services correct than it sounds.
A web server is a good example. Selinux allows more controls.