The other day I had started typing "ls" while sshed to a RedHat machine
and had only typed the "l" when I suddenly decided I needed to switch
away to look at something else. On the Mac, you switch to other
running apps with Apple-TAB, but I managed to hit the TAB first and
somehow managed to "bounce" it.
Of course the Linux bash shell responded as it should have, listing
"l" commands for me. As it also beeps after the first tab, and as
I was expecting to switch away, naturally the list caught my attention more
than it might have otherwise. This happened to be an older
machine so the "l" list was short enough to just display without
asking me if I really wanted to see all the possibilities. If it
hadn't been, I probably just would have said "N". But there
they were, "l" commands.
Two of them caught my eye: "lchfn" and "lchsh". What the heck
are those, I wondered?
Neither had man pages and when I tried "lchfn --help" it wasn't
very helpful. Attempting "lchfn -i" asked for a password but
wouldn't authenticate me. I decided it was time to get back to
whatever it was I had been trying to do before this side trip.
However, I remembered that, and later in the day I logged into
a new Fedora Core 5 box. This had the same two commands and a few
more: luseradd and luserdel were two I noticed right away. The Fedora
also had man pages, but these were even more puzzling. The commands
obviously served the same functions as their equivalents without
the leading "l", but the man pages were much shorter. And there was
another difference: at the end of each man page, where other commands
might say "System Management Command" and a date, these all said "libuser".
Huh? What's "libuser"?
A visit to /usr/share/doc/libuser-0.54 enlightened me a little,
as did the accidental discovery of libuser.conf in /etc. Apparently
libuser is RedHat's attempt to bring user management tasks under
one unifying library. The docs say:
The libuser library implements a standardized interface for manipulating and administering user and group accounts. The library uses pluggable back-ends to interface to its data sources. Sample applications modeled after those included with the shadow password suite are included.
It makes sense to consolidate this stuff , and a search of Google
seems to show that other distros may be picking up on this as well:
there's a Debian version and you'll find "libuser-perl" in Ubuntu
(I'm not certain that's directly related but it definitely serves
the same function).
So the question is: are we supposed to be using this stuff? Apparently
higher level tools may use this library: I think I'm reading correctly
that RedHat's text and gui tools call routines from libuser. Should
"luseradd" replace "useradd"?
Apparently not quite yet. The README on FC5 says:
This package is still under development, but the API
appears to have settled to the point where it's reasonable
to write applications with it.
So, the mystery of "lchfn" and "lchsh" was solved. The
"libuser" concept is apparently still in progress, but
may be completely deployed someday.
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© 2009-11-07 Anthony Lawrence