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