Jeff Waugh wrote:
I'm working on migrating as POS system (1000s systems, worldwide) from RH9
to ubuntu. Unless I can reverse the run level stuff, I can't use it!
Consider: a box boots as 1) a thin client 2) a thick client 3) a stand
alone order taker 4) A manager PC. Elegantly handled by run levels,
different services in different runlevels corresponding to the different
roles.
This really doesn't appear to be a problem that runlevels elegantly solve,
though they are a hammer you could use for that nail if you wanted to. I'd
have to ask why you'd want a single machine to be used in such different
contexts - it sounds like a theoretical use case to me. Points one and two
are configuration cases, and something that your display manager can solve.
Points three and four are modes of use, which can be solved by maintaining
appropriate user (or functional) accounts. Indeed, you could solve all four
at once by running separate, secured X servers if that was your fancy! If
you'd like assistance integrating Ubuntu into your POS deployment plan, let
me know.
The POS scenario is not an artificial use case for System V init
scripts. The whole point of System V init was to allow the
easy use of UNIX in AT&T's CSS telephony switch. In the typical
System V scheme:
0 shutdown to system monitor
s single user
1 s with getty
2 multiuser, no network, no GUI
3 multiuser, no GUI
4 turnkey systems
5 multiuser, GUI
6 shutdown + reboot
So you set your telephone switch application (or POS system) to
use at run level 4 when deployed in production.
When developing or debugging you can boot the system into run
level 5 so that the usual system tools are available.
AT&T wanted to limit the number of special "development" or
"test" accounts, as that was the major source of unapproved
access to the previous generation of switches.
The problem with using a login manager is launching daemons --
perhaps more relevant to telephone switching rather than a POS
system. And you need to run X, which isn't desirable at the
back end where you'd much rather have a serial console.
Cheers,
Glen
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