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