Re: DVORAK and ro

[Jeff Licquia <jeff@luci.org>]

On 30 Apr, Cloudmaster wrote:
> 
> On Fri, 30 Apr 1999, Steven Pritchard wrote:
>> Cloudmaster said:
> 
>> > Also, I wanna set up a system that mounts all filesystems as read-only.  For
>> > some reason, this appears to cause all sorts of problems.  Anyone know of a
>> > good reference to look at that would explain stuff related to booting?
>> 
>> Maybe you should see how the Linux router people are handling that
>> sort of thing.
> 
> Do you guys know of any floppy-based distribs that include perl?  

Perl is a bit on the big side for including in floppy distros,
unfortunately.

One thing I've seen with read-only filesystems: use a ramdisk for root.
There's a HOWTO for that somewhere, as I recall.  It sucks lots of
memory, but memory is cheap these days, and with fancy symlinking you
can probably trim down the requirements.  If you use something like
Tom's for a base system, you could do very well with an 8MB ramdisk.

>> > Alternatively, does anyone know of a way to start a clean shutdown whenever
>> > a power source goes away?  Like, if I had a power inverter hooked up to a
>> > constant 12V source, and wanted the machine to start up whenever I turn on
>> > the car and then shut down neatly when I turn the car off?  Maybe even
>> > switching off a latching relay on succesful shutdown and switching on said
>> > relay when 12V is again applied at the turn of a key?  Just as an example...
>> 
>> Sounds like you need a small UPS with a serial connector.
> 
> I was loking for a solution that would be easier to make with a soldering
> iron and keyboard than with a credit card, but that does sound reasonable.
> I'm considering runing one of the UPS daemons and just sending a power-off
> message to the serial port (it's usualy just a given pin that goes from high
> to low, IIRC).  I'll have to switch to an ATX power supply then and do
> something that'll both send a pulse to the power-on on the motherboard when
> power's applied to the ignition.  It ends up that I'd need like a starter
> switch kind of thing because I want the power inverter to come on when the
> ignition is turned on, and I want the power inverter to remain powered until
> the computer is completely shut down (or at least the disks are unmounted
> cleanly).  Mounting everything read-only would prolly be easier...  If I had
> room under the dash for a UPS, that'd be great though.  Did you have a
> specific UPS that is real small and has a linux-able serial control port in
> mind?

I remember that the empeg guy (the guy now working on building car MP3
players) was talking about this problem somewhere.  I can't remember
his exact solution, but I remember reading about a root ramdisk system
(see above), as well as some kind of capacitor and a sensor attached to
the ignition.  The former system would simply cut power immediately to
the system, while the latter relied on careful measurement of how long
it takes to remount all disks read-only (sensor flags power-off
situation, daemon immediately kills all MP3 player processes and
remounts necessary disks read-only, & we all hope that the capacitor
has enough juice).

Not that I'd know what I'm talking about...



--
To unsubscribe, send email to majordomo@luci.org with
"unsubscribe luci-discuss" in the body.