Here is how it works on my machine (IBM A22e laptop):
Make sure that the apm daemon is started by taking a look at:
(uncomment the apm daemon section if necessary)
If the apm daemon has already been launched, you can check its presence by typing the following:
$ sudo ps -faxu | grep apm
root 36 0.0 0.0 0 0 ? SW Jul08 0:00 [kapmd]
root 686 0.0 0.1 1356 524 ? S Jul08 0:00 /usr/sbin/apmd
You can also try the dmesg command to make sure it was launched properly when the 'puter was switched on.
Then, as root, simply enter:
However, you need to know that some machines have severely broken BIOS, that do *not* conform to the APM/ACPI standards. On such machines, the commands shown above probably won't work...
Off-topic: don't bother compiling a new kernel for your machine if you can upgrade using the kernel 2.4.21 packages from Slackware. I used this package on my machine, and apm support is compiled right in.
Hope this helps...