not quite a dependency

Gerard Beekmans gerard at linuxfromscratch.org
Sat Jun 3 22:52:41 PDT 2000


> Are there other important apps that have these not quite dependency
> relationships?

I had a similar thing while running fetchmail. It would not work at all.
It ran a bit, it prints one dot so it received something but would hang.
Took me a while to figure out why it wasn't working. I sent a test email
to localhost and it worked (because mutt runs sendmail directory and
doesn't try to connect to a port so I wasn't aware for a couple of hours
that sendmail wasn't running right then. /etc/init./sendmail start
solved it).

There are actually quite a few of those not-so-dependency-dependencies
(to throw in a analogy like your distributionless distribution ;o).
XFree86 for example needs at least network support in the kernel. If you
have a standalone machine (no ppp either) you might disable unix domain
sockets and such toys and find that X doens't run (it probably gives a
sensible error like "no available unix domain sockets" and might even
say to recompile your kernel but that's besides the point).

A dependency I found out a few days ago: serial support must be enabled
in kernel to be able to use a modem. I have been running Linux on a
notebook for so long I never thought about it. PCMCIA driver had it's
own serial driver apparently because I always had it disabled in the
kernel. Kernel help said I probably wouldn't need it if I didn't hook
anything up at the serial port. I thought the meant the physical ports
on the back of the system. Couldn't figure out for a while why setserial 
didn't want to bind my modem's IRC and I/O to /dev/ttyS3. Kept saying no
such device. Then it dawned on me...

These actually are interesting things to figure out. If you never change
your kernel, or if you actually have something on your serial port (ie:
an old serial mouse) you might not know or simply realize that the modem
uses that same driver and thus you can be stunned for a few minutes when
you get a PS/2 mouse and disable your serial ports and with it your
modem ports.

Would this be something worth mentioning in the book? Going in depth
would be too much I'm afraid but a note somewhere to most obvious things
could be helpful (again my recent kernel example, enable serial port
support if you use a modem. I know, it sounds so obvious but I really
thought just about the ports at the back of the system and never about
the modem).



-- 
Gerard Beekmans
www.linuxfromscratch.org

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