Messages in this thread | | | From | Sergey Meirovich <> | Date | Mon, 3 Feb 2014 17:33:39 +0200 | Subject | SysRQ via serial console doesn't work for VMWare guests |
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Hi,
I have tried to utilize SysRQ via serial console in VMWare environment: From what I've seen RS-232 Break + <KEY> just doesn't work for 3.13.1 for VMWare guests:
[root@dca-eccs-sbx-db2 ~]# cat /proc/tty/driver/serial serinfo:1.0 driver revision: 0: uart:16550A port:000003F8 irq:4 tx:10034 rx:1 RTS|CTS|DTR|DSR|CD 1: uart:16550A port:000002F8 irq:3 tx:0 rx:0 CTS|DSR|CD 2: uart:unknown port:000003E8 irq:4 3: uart:unknown port:000002E8 irq:3 [root@dca-eccs-sbx-db2 ~]#
Kernel console messages are visible just fine. But SysRQ over serial is not working.
What I have tried to issue break is: 1) screen Control-a b (first VM serial port connected to second VM serial port)) 2) minicom Ctrl-a f (first VM serial port connected to second VM serial port) 3) telnet - ctrl + ] "send brk" from virtual serial port concentrator.
All three above seem like really sending break, though any SysRQ command neither after 5 seconds as stated in documentation nor immediately is producing any result.
Have anyone succeed to use SysRQ over serial with WMWare guests?
I have already opened Red Hat case for that. Their responce was:
"...I think this only works on real physical serial ports. From the kernel docs: On the serial console (PC style standard serial ports only) - You send a BREAK, then within 5 seconds a command key. Sending BREAK twice is interpreted as a normal BREAK. https://www.kernel.org/doc/Documentation/sysrq.txt
An RS-232 BREAK is a period of no electricity on the wire. That's rather difficult to do in a software-only virtual environment..."
I have found that explanation a bit strange.
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