Hi,
I want to implement warm restart in the embedded linux system: re-initialize user space applications without rebooting - that is, the kernel loaded in the system should remain loaded.
Is there a known mechanism in linux to do that?
FYI, my kernel version is 2.6.5.
In case you need details, let me know.

Thanks,
sanyals

Many UNIX system services ("daemons") provide for a mechanism of re-starting themselves. The usual mechanism is through signal handling. Simply send the "SIGHUP", or "1", signal to the process and it will (assuming it has been written this way) restart itself. To send this signal, use the "kill" command.

kill -1 pid

If the daemon does not "handle" the signal in this way, it will likely be killed. In that case, you will need to restart the daemon "by hand".

Some daemons that notably do not restart themselves include:

DHCP (from ISC)
YPSERV, YPBIND

Most "interactive" processes will terminate when you send the HUP signal.

Great! But my system is as follows:

1. There's only one process in the system and all the applications in the system are as threads in this process.
2. I don't support signal handling!
3. FYI, it's an embedded system - not a desktop one.

Also, even if I succeed to re-init the user space program, how do I re-sync with the kernel again. Is there a standardized technique to do that? Or, I have to do it in a proprietary way.

Thanks,
sanyals