I don’t know RHEL so I can only guess the reasons of your problem.
If you use GRUB add at the end of kernel line that parameter:
If you use LILO add to the append parameter that option:
append=" vt.default_utf8=0 resume=/dev/sda4 acpi_sleep=s3_bios,s3_mode"
And then reload lilo program.
Finally reboot your machine.
Now try that command once again:
echo -n mem > /sys/power/state
Assuming suspend works in your system you can install acpi-sleep to use nice script for suspending. You’ll find that program here: http://people.redhat.com/vanhoof/acpi-suspend/RPM/
. Download it and run the command:
rpm -ivh acpi-sleep-*
In result you’ll find these new files in your system:
After reloading ACPI sleep.sh should perform the appropriate actions in different situations, for example when you’ll close the lid of your laptop.
If suspend doesn’t still work it can be kernel configuration issue. Make sure that all these options are enabled in your kernel:
Processor type and features
* Support for suspend on SMP and hot-pluggable CPUs
Power management options
* Suspend to RAM and standby
* Hibernation (aka 'suspend to disk')
* ACPI (Advanced Configuration and Power Interface) Support
If necessary compile and install a new kernel.
If all above will fail ask your question in Red Hat forum: http://www.linuxquestions.org/questions/red-hat-31/
. In your post describe what you did and what happened.