Linux has the "magic sysrq key" to reboot frozen machines remotely, and it works over the serial console, but what about FreeBSD? Is there a way to send a "control-alt-delete" to FreeBSD servers on serial consoles?


Assuming you have a kernel with the debugger option compiled in you can use ControlAltEscape. From there you can call boot(0) or panic.

Chapter 10 of the FreeBSD developers handbook explains this in a lot more detail.

So much for more or less the same as SysReq via a keyboard. On the serial console, you need to send the break signal and have the options BREAK_TO_DEBUGGER enabled. But "it is not the default since there are a lot of serial adapters around that gratuitously generate a BREAK condition, for example when pulling the cable".

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  • chapter 10 of the freebsd handbook is about printing, did you mean chapter 10 of the developers handbook? – anarcat Oct 26 '13 at 21:58
  • Aye. I did. I was linking to both the normal handbook and the lin you posted, then I cleaned it up. I guess I got sidetracked during that. Thanks for noticing. – Hennes Oct 27 '13 at 16:52
  • so i tried it, and it doesn't work from the serial console, it seems that you need to send a BREAK and have the options BREAK_TO_DEBUGGER in your kernel config. – anarcat Oct 29 '13 at 15:31

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