xref: /openbmc/u-boot/doc/README.NetConsole (revision 445277b9)
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
9CONFIG_NETCONSOLE_BUFFER_SIZE - Override the default buffer size
10
11We use an environment variable 'ncip' to set the IP address and the
12port of the destination. The format is <ip_addr>:<port>. If <port> is
13omitted, the value of 6666 is used. If the env var doesn't exist, the
14broadcast address and port 6666 are used. If it is set to an IP
15address of 0 (or 0.0.0.0) then no messages are sent to the network.
16The source / listening port can be configured separately by setting
17the 'ncinport' environment variable and the destination port can be
18configured by setting the 'ncoutport' environment variable.
19
20For example, if your server IP is 192.168.1.1, you could use:
21
22	=> setenv nc 'setenv stdout nc;setenv stdin nc'
23	=> setenv ncip 192.168.1.1
24	=> saveenv
25	=> run nc
26
27
28On the host side, please use this script to access the console:
29
30	tools/netconsole <ip> [port]
31
32The script uses netcat to talk to the board over UDP.  It requires you to
33specify the target IP address (or host name, assuming DNS is working). The
34script can be interrupted by pressing ^T (CTRL-T).
35
36Be aware that in some distributives (Fedora Core 5 at least)
37usage of nc has been changed and -l and -p options are considered
38as mutually exclusive. If nc complains about options provided,
39you can just remove the -p option from the script.
40
41It turns out that 'netcat' cannot be used to listen to broadcast
42packets. We developed our own tool 'ncb' (see tools directory) that
43listens to broadcast packets on a given port and dumps them to the
44standard output.  It will be built when compiling for a board which
45has CONFIG_NETCONSOLE defined.  If the netconsole script can find it
46in PATH or in the same directory, it will be used instead.
47
48For Linux, the network-based console needs special configuration.
49Minimally, the host IP address needs to be specified. This can be
50done either via the kernel command line, or by passing parameters
51while loading the netconsole.o module (when used in a loadable module
52configuration). Please refer to Documentation/networking/logging.txt
53file for the original Ingo Molnar's documentation on how to pass
54parameters to the loadable module.
55
56The format of the kernel command line parameter (for the static
57configuration) is as follows:
58
59  netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
60
61where
62
63  src-port	source for UDP packets
64		(defaults to 6665)
65  src-ip	source IP to use
66		(defaults to the interface's address)
67  dev		network interface
68		(defaults to eth0)
69  tgt-port	port for logging agent
70		(defaults to 6666)
71  tgt-ip	IP address for logging agent
72		(this is the required parameter)
73  tgt-macaddr	ethernet MAC address for logging agent
74		(defaults to broadcast)
75
76Examples:
77
78  netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
79
80or
81
82  netconsole=@/,@192.168.3.1/
83
84Please note that for the Linux networked console to work, the
85ethernet interface has to be up by the time the netconsole driver is
86initialized. This means that in case of static kernel configuration,
87the respective Ethernet interface has to be brought up using the "IP
88Autoconfiguration" kernel feature, which is usually done by defaults
89in the ELDK-NFS-based environment.
90
91To browse the Linux network console output, use the 'netcat' tool invoked
92as follows:
93
94	nc -u -l -p 6666
95
96Note that unlike the U-Boot implementation the Linux netconsole is
97unidirectional, i. e. you have console output only in Linux.
98