Underscores in some directory user, group names (Postfix MacPort example)

[Tabitha McNerney]

Hello Jordan, et al:

Today I was reading my documentation for running a separate OpenLDAP daemon
on an Xserve running Leopard Server. I installed the openldap MacPort (which
is based on OpenLDAP version 2.3.35) and I was somewhat surprised that the
installation created a user with short name "ldap" and a UID of 500 (with a
group short name of "ldap" and a gid of 502). The reason this surprised me
is that Apple ships with Leopard Server a compilation instance of OpenLDAP
2.3.27 which is of course the basis for OpenDirectory, and which slapd
daemon is run by root apparently at boot time (I presume there is a launchd
plist for this but I haven't looked yet).

Now, therefore, considering the logic of using underscores as prefixes to
avoid namespace collisions since the founders of Unix didn't consider this
to be a problem in the 1970s / 1980s, and considering the examples of uids
and gids whose corresponding short names that reside in the local domain
directory that Apple ships with Leopard Server are, in examples:

_postfix
_postdrop
_guest
_xgridagent
_spotlight
_mysql
_svn
_www
_jabber
_sshd

and the list goes on ...

Why oh why do I not see (when I search the local directory domain of my
Leopard Server 10.5.1 instance using WorkgGroup Manager to search on names
with underscores in them):

_ldap ???

Am I out of my mind that the ommission of "_ldap" is illogical and without
basis and is inconsistent with the namespace issue that has been raised
herein this discussoin thread thus far? Would it not be possible, for
example, for a person to accidentally choose a short user name of "ldap"
just as they might also accidentally do so with a name such as "postfix"?
Why does life have to be so complicated -- meaning, why do humans create
their own unnecessary complexity? We have too many rules we have to
remember. Where oh where is my missing friend in Leopard's local directory
domain named, "_ldap"? Thus as a result, the openldap MacPort created a
separate user account named "ldap". Ugh!

Thanks,

T.M.

On 1/5/08, Tabitha McNerney <tabithamc at gmail.com> wrote:
>
>
>
> On 1/4/08, Jordan K. Hubbard <jkh at apple.com> wrote:
> >
> > This is because the original designers of Unix neglected to take into
> > account the notion of user namespaces - the namespace is flat.  That
> > means that system or role specific names can conflict with names that
> > users would like to use for themselves ( c.f. "admin" or "operator")
> > unless you adopt a convention for keeping them separate.  That
> > convention is the prefix underscore.
> >
> > - Jordan
>
>
> Jordan,
>
> Thank you very much. Makes perfect sense. Its hard to find fault with the
> original designers of Unix (they probably never would have guessed, decades
> later, that individuals in the comfort of their own homes would run Unix on
> a machine that sits in their lap)!
>
> Best,
>
> T.M.
>
> On Jan 4, 2008, at 5:29 PM, Tabitha McNerney wrote:
> >
> > > Hello all --
> > >
> > > I just installed the current version of the Postfix port (version
> > > 2.4.6) on a Leopard Server system.
> > >
> > > After the install, I noticed a username and group name of "_postfix"
> > > and "_postdrop" respectively, as in:
> > > drwx--x---  2 _postfix  _postdrop  102 Jan  4 23:06 public/
> > > drwx-wx---  2 _postfix  _postdrop  102 Jan  4 23:06 maildrop/
> > > This differs from previous Postfix port installations (UID 27 was
> > > "postfix" not "_postfix"). This isn't really a MacPorts specific
> > > issue but I'm wondering if anyone knows why Apple changed their
> > > naming schema on Leopard, for short names such as:
> > >
> > > from "postfix" to "_postfix"
> > >
> > > ?
> > >
> > > I wonder if this has something to do with becoming fully UNIX
> > > compliant? POSIX?
> > >
> > > Mr. Jordan Hubbard, can you offer some wisdom and perspective on
> > > this subject?
> > >
> > > Thank you,
> > >
> > > T.M.
> > >
> >
> >
>
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