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In U-Boot, we implemented the networked console via the standard
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"devices" mechanism, which means that you can switch between the
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serial and network input/output devices by adjusting the 'stdin' and
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'stdout' environment variables. To switch to the networked console,
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set either of these variables to "nc". Input and output can be
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switched independently.
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CONFIG_NETCONSOLE_BUFFER_SIZE - Override the default buffer size
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We use an environment variable 'ncip' to set the IP address and the
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port of the destination. The format is <ip_addr>:<port>. If <port> is
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omitted, the value of 6666 is used. If the env var doesn't exist, the
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broadcast address and port 6666 are used. If it is set to an IP
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address of 0 (or 0.0.0.0) then no messages are sent to the network.
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The source / listening port can be configured separately by setting
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the 'ncinport' environment variable and the destination port can be
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configured by setting the 'ncoutport' environment variable.
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For example, if your server IP is 192.168.1.1, you could use:
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=> setenv nc 'setenv stdout nc;setenv stdin nc'
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=> setenv ncip 192.168.1.1
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=> saveenv
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=> run nc
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On the host side, please use this script to access the console:
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tools/netconsole <ip> [port]
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The script uses netcat to talk to the board over UDP. It requires you to
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specify the target IP address (or host name, assuming DNS is working). The
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script can be interrupted by pressing ^T (CTRL-T).
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Be aware that in some distributives (Fedora Core 5 at least)
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usage of nc has been changed and -l and -p options are considered
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as mutually exclusive. If nc complains about options provided,
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you can just remove the -p option from the script.
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It turns out that 'netcat' cannot be used to listen to broadcast
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packets. We developed our own tool 'ncb' (see tools directory) that
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listens to broadcast packets on a given port and dumps them to the
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standard output. It will be built when compiling for a board which
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has CONFIG_NETCONSOLE defined. If the netconsole script can find it
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in PATH or in the same directory, it will be used instead.
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For Linux, the network-based console needs special configuration.
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Minimally, the host IP address needs to be specified. This can be
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done either via the kernel command line, or by passing parameters
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while loading the netconsole.o module (when used in a loadable module
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configuration). Please refer to Documentation/networking/logging.txt
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file for the original Ingo Molnar's documentation on how to pass
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parameters to the loadable module.
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The format of the kernel command line parameter (for the static
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configuration) is as follows:
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netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
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where
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src-port source for UDP packets
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(defaults to 6665)
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src-ip source IP to use
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(defaults to the interface's address)
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dev network interface
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(defaults to eth0)
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tgt-port port for logging agent
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(defaults to 6666)
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tgt-ip IP address for logging agent
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(this is the required parameter)
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tgt-macaddr ethernet MAC address for logging agent
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(defaults to broadcast)
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Examples:
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netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
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or
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netconsole=@/,@192.168.3.1/
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Please note that for the Linux networked console to work, the
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ethernet interface has to be up by the time the netconsole driver is
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initialized. This means that in case of static kernel configuration,
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the respective Ethernet interface has to be brought up using the "IP
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Autoconfiguration" kernel feature, which is usually done by defaults
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in the ELDK-NFS-based environment.
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To browse the Linux network console output, use the 'netcat' tool invoked
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as follows:
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nc -u -l -p 6666
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Note that unlike the U-Boot implementation the Linux netconsole is
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unidirectional, i. e. you have console output only in Linux.
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