[PATCH] adduser: remove preconfigured GECOS full name field

[tito]

On Mon, 18 Nov 2024 22:05:28 +0100
Xabier Oneca  --  xOneca <xoneca at gmail.com> wrote:

> Hi 'fossd',
> 
> > Pre-configuring "Linux User" as Full Name is confusing a lot of users
> > downstream.[1] For example, in geary e-mails were sent out as "Linux
> > User"[2] and I also saw a couple of git commits with this name. This name
> > does not bring any more improvements than just leaving this field
> > empty, and let applications most likely fallback to the username.
> >
> > Alternative would be to set the field to `&` (Capitalized username,
> > according to passwd(5)) or that we just set the GECOS field downstream.
> >
> > [1] https://gitlab.postmarketos.org/postmarketOS/pmbootstrap/-/issues/2214
> > [2] https://gitlab.gnome.org/GNOME/geary/-/issues/1486
> >
> > Signed-off-by: fossdd <fossdd at pwned.life>
> > ---
> >  loginutils/adduser.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/loginutils/adduser.c b/loginutils/adduser.c
> > index d3c795afa..c0dc845a2 100644
> > --- a/loginutils/adduser.c
> > +++ b/loginutils/adduser.c
> > @@ -196,7 +196,7 @@ int adduser_main(int argc UNUSED_PARAM, char **argv)
> >                 bb_simple_error_msg_and_die(bb_msg_perm_denied_are_you_root);
> >         }
> >
> > -       pw.pw_gecos = (char *)"Linux User,,,";
> > +       pw.pw_gecos = (char *)",,,";
> 
> I would just, as well, leave the GECOS field entirely empty for that
> effect. The commas do not contribute anything useful.
> 
> Cheers,
> 
> Xabier Oneca_,,_

Hi,
man 5 passwd says:

" The comment field, also known as the gecos field, is used by various system utilities, such as finger(1). 
   The use of an ampersand here will be replaced by the capitalised login name when the field is used or displayed by
   such system utilities."

and in Wikipedia:

"The gecos field, or GECOS field, is a field in each record in the /etc/passwd file on Unix and similar operating systems. On UNIX, it is the 5th of 7 fields in a record.

It is typically used to record general information about the account or its user(s) such as their real name and phone number.
Format

The typical format for the GECOS field is a comma-delimited list with this order:

    1) User's full name (or application name, if the account is for a program)
    2) Building and room number or contact person
    3) Office telephone number
    4) Home telephone number
    5) Any other contact information (pager number, fax, external e-mail address, etc.)

In most UNIX systems non-root users can change their own information using the chfn or chsh command. "

Where GECOS are divided as:

:FullName,RoomAddress,WorkPhone,HomePhone,Others:

And Others are divided in as many commas as you like:

:FullName,RoomAddress,WorkPhone,HomePhone,Other1,Other2,Other3:


For the record : GECOS  stands for "General Electric Comprehensive Operating System".

So I would suggest one ampersand and four commas:

pw.pw_gecos = (char *)"&,,,,";

but acceptable would also be:

pw.pw_gecos = (char *)"&";

for the sake of space saving because the finger client command which is the
de facto authoritative source of information for gecos field formatting
nowadays (together with sendmail) follows this rules in most Unix-like OS:


 1) Ampersands should only be expanded in the first comma-delimited subfield (i.e. the so-called "full name" or "real name" subfield). 
 
 2) If there are no commas in the GECOS field, treat the entire field as the real name.

 3)  Any and all ampersands are expanded, not only the first one.

  4) If the first character of the username is an ASCII lowercase letter, that letter is uppercased in the ampersand expansion. 
      Otherwise it is left intact. No case conversion is done to characters other than the first one.

Even better to be picky  would be ampersand for normal users and empty gecos as default for system users.

Ciao,
Tito