1 2 In U-Boot, we implemented the networked console via the standard 3 "devices" mechanism, which means that you can switch between the 4 serial and network input/output devices by adjusting the 'stdin' and 5 'stdout' environment variables. To switch to the networked console, 6 set either of these variables to "nc". Input and output can be 7 switched independently. 8 9 CONFIG_NETCONSOLE_BUFFER_SIZE - Override the default buffer size 10 11 We use an environment variable 'ncip' to set the IP address and the 12 port of the destination. The format is <ip_addr>:<port>. If <port> is 13 omitted, the value of 6666 is used. If the env var doesn't exist, the 14 broadcast address and port 6666 are used. If it is set to an IP 15 address of 0 (or 0.0.0.0) then no messages are sent to the network. 16 The source / listening port can be configured separately by setting 17 the 'ncinport' environment variable and the destination port can be 18 configured by setting the 'ncoutport' environment variable. 19 20 For 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 28 On the host side, please use this script to access the console: 29 30 tools/netconsole <ip> [port] 31 32 The script uses netcat to talk to the board over UDP. It requires you to 33 specify the target IP address (or host name, assuming DNS is working). The 34 script can be interrupted by pressing ^T (CTRL-T). 35 36 Be aware that in some distributives (Fedora Core 5 at least) 37 usage of nc has been changed and -l and -p options are considered 38 as mutually exclusive. If nc complains about options provided, 39 you can just remove the -p option from the script. 40 41 It turns out that 'netcat' cannot be used to listen to broadcast 42 packets. We developed our own tool 'ncb' (see tools directory) that 43 listens to broadcast packets on a given port and dumps them to the 44 standard output. It will be built when compiling for a board which 45 has CONFIG_NETCONSOLE defined. If the netconsole script can find it 46 in PATH or in the same directory, it will be used instead. 47 48 For Linux, the network-based console needs special configuration. 49 Minimally, the host IP address needs to be specified. This can be 50 done either via the kernel command line, or by passing parameters 51 while loading the netconsole.o module (when used in a loadable module 52 configuration). Please refer to Documentation/networking/logging.txt 53 file for the original Ingo Molnar's documentation on how to pass 54 parameters to the loadable module. 55 56 The format of the kernel command line parameter (for the static 57 configuration) is as follows: 58 59 netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr] 60 61 where 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 76 Examples: 77 78 netconsole=4444 (a] 10.0.0.1/eth1,9353 (a] 10.0.0.2/12:34:56:78:9a:bc 79 80 or 81 82 netconsole=@/,@192.168.3.1/ 83 84 Please note that for the Linux networked console to work, the 85 ethernet interface has to be up by the time the netconsole driver is 86 initialized. This means that in case of static kernel configuration, 87 the respective Ethernet interface has to be brought up using the "IP 88 Autoconfiguration" kernel feature, which is usually done by defaults 89 in the ELDK-NFS-based environment. 90 91 To browse the Linux network console output, use the 'netcat' tool invoked 92 as follows: 93 94 nc -u -l -p 6666 95 96 Note that unlike the U-Boot implementation the Linux netconsole is 97 unidirectional, i. e. you have console output only in Linux. 98
