xref: /openbmc/u-boot/doc/README.NetConsole (revision 236aad87)
1
2In U-Boot, we implemented the networked console via the standard
3"devices" mechanism, which means that you can switch between the
4serial and network input/output devices by adjusting the 'stdin' and
5'stdout' environment variables. To switch to the networked console,
6set either of these variables to "nc". Input and output can be
7switched independently.
8
9We use an environment variable 'ncip' to set the IP address and the
10port of the destination. The format is <ip_addr>:<port>. If <port> is
11omitted, the value of 6666 is used. If the env var doesn't exist, the
12broadcast address and port 6666 are used. If it is set to an IP
13address of 0 (or 0.0.0.0) then no messages are sent to the network.
14
15For example, if your server IP is 192.168.1.1, you could use:
16
17	=> setenv nc 'setenv stdout nc;setenv stdin nc'
18	=> setenv ncip 192.168.1.1
19	=> saveenv
20	=> run nc
21
22
23On the host side, please use this script to access the console:
24
25	tools/netconsole <ip> [port]
26
27The script uses netcat to talk to the board over UDP.  It requires you to
28specify the target IP address (or host name, assuming DNS is working). The
29script can be interrupted by pressing ^T (CTRL-T).
30
31Be aware that in some distributives (Fedora Core 5 at least)
32usage of nc has been changed and -l and -p options are considered
33as mutually exclusive. If nc complains about options provided,
34you can just remove the -p option from the script.
35
36It turns out that 'netcat' cannot be used to listen to broadcast
37packets. We developed our own tool 'ncb' (see tools directory) that
38listens to broadcast packets on a given port and dumps them to the
39standard output. use it as follows:
40
41+++++++++++++++++++++++++++++++++++++++++++
42#! /bin/bash
43
44[ $# = 1 ] || { echo "Usage: $0 target_ip" >&2 ; exit 1 ; }
45TARGET_IP=$1
46
47stty icanon echo intr ^T
48./ncb &
49nc -u ${TARGET_IP} 6666
50stty icanon echo intr ^C
51kill 0
52+++++++++++++++++++++++++++++++++++++++++++
53
54Again, this script takes exactly one argument, which is interpreted
55as the target IP address (or host name, assuming DNS is working). The
56script can be interrupted by pressing ^T (CTRL-T).
57
58The 'ncb' tool can be found in the tools directory; it will be built
59when compiling for a board which has CONFIG_NETCONSOLE defined.
60
61For Linux, the network-based console needs special configuration.
62Minimally, the host IP address needs to be specified. This can be
63done either via the kernel command line, or by passing parameters
64while loading the netconsole.o module (when used in a loadable module
65configuration). Please refer to Documentation/networking/logging.txt
66file for the original Ingo Molnar's documentation on how to pass
67parameters to the loadable module.
68
69The format of the kernel command line parameter (for the static
70configuration) is as follows:
71
72  netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
73
74where
75
76  src-port	source for UDP packets
77		(defaults to 6665)
78  src-ip	source IP to use
79		(defaults to the interface's address)
80  dev		network interface
81		(defaults to eth0)
82  tgt-port	port for logging agent
83		(defaults to 6666)
84  tgt-ip	IP address for logging agent
85		(this is the required parameter)
86  tgt-macaddr	ethernet MAC address for logging agent
87		(defaults to broadcast)
88
89Examples:
90
91  netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
92
93or
94
95  netconsole=@/,@192.168.3.1/
96
97Please note that for the Linux networked console to work, the
98ethernet interface has to be up by the time the netconsole driver is
99initialized. This means that in case of static kernel configuration,
100the respective Ethernet interface has to be brought up using the "IP
101Autoconfiguration" kernel feature, which is usually done by defaults
102in the ELDK-NFS-based environment.
103
104To browse the Linux network console output, use the 'netcat' tool invoked
105as follows:
106
107	nc -u -l -p 6666
108
109Note that unlike the U-Boot implementation the Linux netconsole is
110unidirectional, i. e. you have console output only in Linux.
111