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+++++++++++++++++++++++++++++++++++++++++++ 26#! /bin/bash 27 28[ $# = 1 ] || { echo "Usage: $0 target_ip" >&2 ; exit 1 ; } 29TARGET_IP=$1 30 31stty -icanon -echo intr ^T 32nc -u -l -p 6666 < /dev/null & 33nc -u ${TARGET_IP} 6666 34stty icanon echo intr ^C 35+++++++++++++++++++++++++++++++++++++++++++ 36 37The script expects exactly one argument, which is interpreted as the 38target IP address (or host name, assuming DNS is working). The script 39can be interrupted by pressing ^T (CTRL-T). 40 41Be aware that in some distributives (Fedora Core 5 at least) 42usage of nc has been changed and -l and -p options are considered 43as mutually exclusive. If nc complains about options provided, 44you can just remove the -p option from the script. 45 46It turns out that 'netcat' cannot be used to listen to broadcast 47packets. We developed our own tool 'ncb' (see tools directory) that 48listens to broadcast packets on a given port and dumps them to the 49standard output. use it as follows: 50 51+++++++++++++++++++++++++++++++++++++++++++ 52#! /bin/bash 53 54[ $# = 1 ] || { echo "Usage: $0 target_ip" >&2 ; exit 1 ; } 55TARGET_IP=$1 56 57stty icanon echo intr ^T 58./ncb & 59nc -u ${TARGET_IP} 6666 60stty icanon echo intr ^C 61kill 0 62+++++++++++++++++++++++++++++++++++++++++++ 63 64Again, this script takes exactly one argument, which is interpreted 65as the target IP address (or host name, assuming DNS is working). The 66script can be interrupted by pressing ^T (CTRL-T). 67 68The 'ncb' tool can be found in the tools directory; it will not be 69built by default so you will ither have to adjust the Makefile or 70build it manually. 71 72 73For Linux, the network-based console needs special configuration. 74Minimally, the host IP address needs to be specified. This can be 75done either via the kernel command line, or by passing parameters 76while loading the netconsole.o module (when used in a loadable module 77configuration). Please refer to Documentation/networking/logging.txt 78file for the original Ingo Molnar's documentation on how to pass 79parameters to the loadable module. 80 81The format of the kernel command line parameter (for the static 82configuration) is as follows: 83 84 netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr] 85 86where 87 88 src-port source for UDP packets 89 (defaults to 6665) 90 src-ip source IP to use 91 (defaults to the interface's address) 92 dev network interface 93 (defaults to eth0) 94 tgt-port port for logging agent 95 (defaults to 6666) 96 tgt-ip IP address for logging agent 97 (this is the required parameter) 98 tgt-macaddr ethernet MAC address for logging agent 99 (defaults to broadcast) 100 101Examples: 102 103 netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc 104 105or 106 107 netconsole=@/,@192.168.3.1/ 108 109Please note that for the Linux networked console to work, the 110ethernet interface has to be up by the time the netconsole driver is 111initialized. This means that in case of static kernel configuration, 112the respective Ethernet interface has to be brought up using the "IP 113Autoconfiguration" kernel feature, which is usually done by defaults 114in the ELDK-NFS-based environment. 115 116To browse the Linux network console output, use the 'netcat' tool invoked 117as follows: 118 119 nc -u -l -p 6666 120 121Note that unlike the U-Boot implementation the Linux netconsole is 122unidirectional, i. e. you have console output only in Linux. 123