Ubuntu – How to use Magic SysRq Key, if theres no SysRq key on the keyboard

sysrq

According to this it's very important.
What I can do?
Can I rebind this key to something else?

As ravery said, your "Print Screen" key should work.

"SysReq" is often not spelt out on small laptop keyboards, but it is still that key.

The Dell E6420 works as follows

sudo kbd_mode -s -C /dev/tty7

Eventually you have to change the console path, if your X server is running on a different virtual terminal.