The
utility is designed to provide a way for users to access
dcons(4)
(dumb console device) on a local or remote system.
The
utility interacts with
dcons(4)
using
kvm(3)
or
firewire(4),
and interacts with the user over TTY or TCP/IP.
To access remote
dcons(4)
using
firewire(4),
you have to specify target EUI64 address using the
-t
option. Physical DMA should be enabled on the target machine for access
via FireWire.
The
utility and the
dcons(4)
driver communicate using 2 ports, one for the console port and another
for remote
gdb(1)
port.
Users are supposed to access
using TTY,
telnet(1)
and
gdb(1).
You can specify listen ports for console and
gdb(1)
port using the
-C
and
-G
options respectively.
The port number 0 has special meaning that
current TTY (stdin/stdout) is used instead of TCP/IP.
A negative port number will disable the port.
By analogy with
pty(4)
device, the
dcons(4)
acts as a slave device and
acts as a master device with
telnetd(8).
Typed characters are normally transmitted directly to
dcons(4).
A escape character (the default is
`~'
) appearing as the first character of a line is an escape signal; the
following are recognized:
~.
Drop the connection and exit.
~^G
Invoke kgdb on the terminal on which dconschat is running.
~^R
Reset the target over FireWire if a reset address is registered in Configuration ROM.
~^Z
Suspend the dconschat process.
The following options are supported.
-b
Translate Ctrl-C to ALT_BREAK (CR +
`~'
+ Ctrl-B) on
gdb(1)
port.
Listen on a wildcard address rather than localhost.
-R
Read-only.
Do not write anything to the
dcons(4)
buffer.
-T
Enable ad-hoc workaround for the TELNET protocol to
remove unnecessary byte sequences.
It should be set when you access
using
telnet(1).
-1
One-shot.
Read available buffer, then exit.
This implies the
-r
option.
-e escape-char
Specify escape character.
The default is '~'.
-h hz
Specify polling rate.
The default value is 100.
-C console_port
Specify the console port.
The default value is 0 (stdin/stdout).
-G gdb_port
Specify
gdb(1)
port.
The default value is -1 (disabled).
-M core
Specify core file.
-N system
Specify system file such as
/boot/kernel/kernel
-t target_eui64
Specify the 64-bit extended unique identifier of the target,
and use FireWire to access remote
dcons(4).
-a address
Specify the physical I/O address of the
dcons(4)
buffer.
See
dcons(4)
for details.
If this option is not specified,
tries to get the address from the Configuration ROM on the target.
You are supposed to enable
dcons_crom4
on the target to omit this option.
-u bus_num
Specify FireWire bus number.
The default is 0.
FILES
/dev/fwmem0.0
/dev/mem
/dev/kmem
EXAMPLES
To use
with FireWire for remote
dcons(4),
you have to specify the EUI64 of the target.
You can obtain EUI64 by running
fwcontrol(8)
without options.
The first EUI64 is of the host running
fwcontrol(8)
and others on the bus follow.
You will get console output of the target and login prompt if a
getty(8)
is running on
dcons(4).
You can break to DDB with ALT_BREAK (CR +
`~'
+ Ctrl-B)
if
DDB
and
ALT_BREAK_TO_DEBUGGER
are enabled in the target kernel.
To quit the session, type CR +
`~'
+
`.'
in the console port.
Using
gdb(1)
port is almost the same as remote
gdb(1)
over serial line except
using TCP/IP instead of
/dev/cu*
See
Sx On-line Kernel Debugging Using Remote GDB
section of
"The FreeBSD Developers Handbook"
and
gdb(4)
for details.
% gdb -k kernel.debug
(kgdb) target remote :12345
Once
gdb(1)
is attached and you specified the
-b
option to
,
typing Ctrl-C in
gdb(1)
causes a break to debugger.
The following command gets the console log from the crash dump:
# dconschat -1 -M vmcore.0 -N kernel.0
If you want access to the console using
telnet(1),
try the following:
# dconschat -rTC 5555 &
# telnet localhost 5555
You may want to keep logging console output of several machines.
conserver-com
in the Ports collection may help you.
Insert the following lines in
conserver.cf
console local {
master localhost;
type exec;
exec /usr/sbin/dconschat -rh 25;
}
console remote {
master localhost;
type exec;
exec /usr/sbin/dconschat -rh 25 -t 00-11-22-33-44-55-66-77;
}
