netconsole.rst 3.8 KB

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  1. Network console
  2. ===============
  3. In U-Boot, we implemented the networked console via the standard
  4. "devices" mechanism, which means that you can switch between the
  5. serial and network input/output devices by adjusting the 'stdin' and
  6. 'stdout' environment variables. To switch to the networked console,
  7. set either of these variables to "nc". Input and output can be
  8. switched independently.
  9. The default buffer size can be overridden by setting
  10. CONFIG_NETCONSOLE_BUFFER_SIZE.
  11. We use an environment variable 'ncip' to set the IP address and the
  12. port of the destination. The format is <ip_addr>:<port>. If <port> is
  13. omitted, the value of 6666 is used. If the env var doesn't exist, the
  14. broadcast address and port 6666 are used. If it is set to an IP
  15. address of 0 (or 0.0.0.0) then no messages are sent to the network.
  16. The source / listening port can be configured separately by setting
  17. the 'ncinport' environment variable and the destination port can be
  18. configured by setting the 'ncoutport' environment variable.
  19. For example, if your server IP is 192.168.1.1, you could use::
  20. => setenv nc 'setenv stdout nc;setenv stdin nc'
  21. => setenv ncip 192.168.1.1
  22. => saveenv
  23. => run nc
  24. On the host side, please use this script to access the console
  25. .. code-block:: bash
  26. tools/netconsole <ip> [port]
  27. The script uses netcat to talk to the board over UDP. It requires you to
  28. specify the target IP address (or host name, assuming DNS is working). The
  29. script can be interrupted by pressing ^T (CTRL-T).
  30. Be aware that in some distributives (Fedora Core 5 at least)
  31. usage of nc has been changed and -l and -p options are considered
  32. as mutually exclusive. If nc complains about options provided,
  33. you can just remove the -p option from the script.
  34. It turns out that 'netcat' cannot be used to listen to broadcast
  35. packets. We developed our own tool 'ncb' (see tools directory) that
  36. listens to broadcast packets on a given port and dumps them to the
  37. standard output. It will be built when compiling for a board which
  38. has CONFIG_NETCONSOLE defined. If the netconsole script can find it
  39. in PATH or in the same directory, it will be used instead.
  40. For Linux, the network-based console needs special configuration.
  41. Minimally, the host IP address needs to be specified. This can be
  42. done either via the kernel command line, or by passing parameters
  43. while loading the netconsole.o module (when used in a loadable module
  44. configuration). Please refer to Documentation/networking/logging.txt
  45. file for the original Ingo Molnar's documentation on how to pass
  46. parameters to the loadable module.
  47. The format of the kernel command line parameter (for the static
  48. configuration) is as follows
  49. .. code-block:: bash
  50. netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
  51. where
  52. src-port
  53. source for UDP packets (defaults to 6665)
  54. src-ip
  55. source IP to use (defaults to the interface's address)
  56. dev
  57. network interface (defaults to eth0)
  58. tgt-port
  59. port for logging agent (defaults to 6666)
  60. tgt-ip
  61. IP address for logging agent (this is the required parameter)
  62. tgt-macaddr
  63. ethernet MAC address for logging agent (defaults to broadcast)
  64. Examples
  65. .. code-block:: bash
  66. netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
  67. netconsole=@/,@192.168.3.1/
  68. Please note that for the Linux networked console to work, the
  69. ethernet interface has to be up by the time the netconsole driver is
  70. initialized. This means that in case of static kernel configuration,
  71. the respective Ethernet interface has to be brought up using the "IP
  72. Autoconfiguration" kernel feature, which is usually done by defaults
  73. in the ELDK-NFS-based environment.
  74. To browse the Linux network console output, use the 'netcat' tool invoked
  75. as follows:
  76. .. code-block:: bash
  77. nc -u -l -p 6666
  78. Note that unlike the U-Boot implementation the Linux netconsole is
  79. unidirectional, i. e. you have console output only in Linux.