--- name: "dconschat" section: "8" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["freebsd"] url: "https://new.carta.tech/dconschat" --- # dconschat(8) user interface to dcons(4) ## NAME **dconschat** – user interface to [dcons(4)](/dcons/4.md) ## SYNOPSIS **dconschat** \[**-brvwRT1**\] \[**-e** *escape-char*\] \[**-h** *hz*\] \[**-C** *console\_port*\] \[**-G** *gdb\_port*\] \[**-M** *core*\] \[**-N** *system*\] **dconschat** \[**-brvwR1**\] \[**-h** *hz*\] \[**-C** *console\_port*\] \[**-G** *gdb\_port*\] \[**-a** *address*\] \[**-u** *bus\_num*\] **-t** *target\_eui64* ## DESCRIPTION The **dconschat** utility is designed to provide a way for users to access [dcons(4)](/dcons/4.md) (dumb console device) on a local or remote system. The **dconschat** utility interacts with [dcons(4)](/dcons/4.md) using [kvm(3)](/kvm/3.md) or [firewire(4)](/firewire/4.md), and interacts with the user over TTY or TCP/IP. To access remote [dcons(4)](/dcons/4.md) using [firewire(4)](/firewire/4.md), 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 **dconschat** utility and the [dcons(4)](/dcons/4.md) driver communicate using 2 ports, one for the console port and another for remote [gdb(1)](/gdb/1.md) (*ports/devel/gdb*) port. Users are supposed to access **dconschat** using TTY, [telnet(1)](/telnet/1.md) and [gdb(1)](/gdb/1.md) (*ports/devel/gdb*). You can specify listen ports for console and [gdb(1)](/gdb/1.md) (*ports/devel/gdb*) 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)](/pty/4.md) device, the [dcons(4)](/dcons/4.md) acts as a slave device and **dconschat** acts as a master device with **telnetd**. Typed characters are normally transmitted directly to [dcons(4)](/dcons/4.md). 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)](/gdb/1.md) (*ports/devel/gdb*) port. - **-r** Replay old buffer on connection. - **-v** Verbose debug output. Multiple **-v** options increase verbosity. - **-w** Listen on a wildcard address rather than localhost. - **-R** Read-only. Do not write anything to the [dcons(4)](/dcons/4.md) buffer. - **-T** Enable ad-hoc workaround for the TELNET protocol to remove unnecessary byte sequences. It should be set when you access **dconschat** using [telnet(1)](/telnet/1.md). - **-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)](/gdb/1.md) (*ports/devel/gdb*) 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)](/dcons/4.md). - **-a** *address* Specify the physical I/O address of the [dcons(4)](/dcons/4.md) buffer. See [dcons(4)](/dcons/4.md) for details. If this option is not specified, **dconschat** tries to get the address from the Configuration ROM on the target. You are supposed to enable [dcons\_crom(4)](/dcons_crom/4.md) 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 **dconschat** with FireWire for remote [dcons(4)](/dcons/4.md), you have to specify the EUI64 of the target. You can obtain EUI64 by running [fwcontrol(8)](/fwcontrol/8.md) without options. The first EUI64 is of the host running [fwcontrol(8)](/fwcontrol/8.md) and others on the bus follow. ``` # fwcontrol 2 devices (info_len=2) node EUI64 status 1 77-66-55-44-33-22-11-00 0 0 00-11-22-33-44-55-66-77 1 ``` The EUI64 does not change unless you change the hardware as the ethernet address. Now we can run **dconschat**. ``` # dconschat -br -G 12345 -t 00-11-22-33-44-55-66-77 ``` You will get console output of the target and login prompt if a [getty(8)](/getty/8.md) is running on [dcons(4)](/dcons/4.md). 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)](/gdb/1.md) (*ports/devel/gdb*) port is almost the same as remote [gdb(1)](/gdb/1.md) (*ports/devel/gdb*) over serial line except using TCP/IP instead of */dev/cu\**. See On-line Kernel Debugging Using Remote GDB section of and [gdb(4)](/gdb/4.md) for details. ``` % gdb -k kernel.debug (kgdb) target remote :12345 ``` Once [gdb(1)](/gdb/1.md) (*ports/devel/gdb*) is attached and you specified the **-b** option to **dconschat**, typing Ctrl-C in [gdb(1)](/gdb/1.md) (*ports/devel/gdb*) 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)](/telnet/1.md), 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; } ``` ## SEE ALSO [gdb(1)](/gdb/1.md) (*ports/devel/gdb*), [telnet(1)](/telnet/1.md), [kvm(3)](/kvm/3.md), [dcons(4)](/dcons/4.md), [dcons\_crom(4)](/dcons_crom/4.md), [ddb(4)](/ddb/4.md), [firewire(4)](/firewire/4.md), [fwohci(4)](/fwohci/4.md), [gdb(4)](/gdb/4.md), [eui64(5)](/eui64/5.md), [fwcontrol(8)](/fwcontrol/8.md) ## AUTHORS Hidetoshi Shimokawa ⟨*simokawa@FreeBSD.org*⟩ ## BUGS This utility is currently under development.