How to force a panic/crash in Linux?

You can evoke a crash/panic by:

echo c > /proc/sysrq-trigger

System can be forced to crash from the console by pressing: "Alt-syrq-c"

What are the command keys and what do they do?

'r'     - Turns off keyboard raw mode and sets it to XLATE.

'k'     - Secure Access Key (SAK) Kills all programs on the current virtual
         console. NOTE: See important comments below in SAK section.

'b'     - Will immediately reboot the system without syncing or unmounting
         your disks.

'c'     - Intentionally crash the system without syncing or unmounting
         your disks.  This is most useful if the NETDUMP client package
         has been installed.

'o'     - Will shut your system off (if configured and supported).

's'     - Will attempt to sync all mounted filesystems.

'u'     - Will attempt to remount all mounted filesystems read-only.

'p'     - Will dump the current registers and flags to your console.

't'     - Will dump a list of current tasks and their information to your
         console.

'm'     - Will dump current memory info to your console.

'0'-'9' - Sets the console log level, controlling which kernel messages
         will be printed to your console. ('0', for example would make
         it so that only emergency messages like PANICs or OOPSes would
         make it to your console.)

'e'     - Send a SIGTERM to all processes, except for init.

'i'     - Send a SIGKILL to all processes, except for init.

'l'     - Send a SIGKILL to all processes, INCLUDING init. (Your system
         will be non-functional after this.)

'h'     - Will display help ( actually any other key than those listed
         above will display help. but 'h' is easy to remember :-)

See sysrq.txt somewhere underneath /usr/src/linux-XXX/Documentation for more information.