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