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-
-started by Ingo Molnar <mingo@redhat.com>, 2001.09.17
-2.6 port and netpoll api by Matt Mackall <mpm@selenic.com>, Sep 9 2003
-
-Please send bug reports to Matt Mackall <mpm@selenic.com>
-and Satyam Sharma <satyam.sharma@gmail.com>
-
-Introduction:
-=============
-
-This module logs kernel printk messages over UDP allowing debugging of
-problem where disk logging fails and serial consoles are impractical.
-
-It can be used either built-in or as a module. As a built-in,
-netconsole initializes immediately after NIC cards and will bring up
-the specified interface as soon as possible. While this doesn't allow
-capture of early kernel panics, it does capture most of the boot
-process.
-
-Sender and receiver configuration:
-==================================
-
-It takes a string configuration parameter "netconsole" in the
-following format:
-
- netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
-
- where
- src-port source for UDP packets (defaults to 6665)
- src-ip source IP to use (interface address)
- dev network interface (eth0)
- tgt-port port for logging agent (6666)
- tgt-ip IP address for logging agent
- tgt-macaddr ethernet MAC address for logging agent (broadcast)
-
-Examples:
-
- linux netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
-
- or
-
- insmod netconsole netconsole=@/,@10.0.0.2/
-
-It also supports logging to multiple remote agents by specifying
-parameters for the multiple agents separated by semicolons and the
-complete string enclosed in "quotes", thusly:
-
- modprobe netconsole netconsole="@/,@10.0.0.2/;@/eth1,6892@10.0.0.3/"
-
-Built-in netconsole starts immediately after the TCP stack is
-initialized and attempts to bring up the supplied dev at the supplied
-address.
-
-The remote host can run either 'netcat -u -l -p <port>',
-'nc -l -u <port>' or syslogd.
-
-Dynamic reconfiguration:
-========================
-
-Dynamic reconfigurability is a useful addition to netconsole that enables
-remote logging targets to be dynamically added, removed, or have their
-parameters reconfigured at runtime from a configfs-based userspace interface.
-[ Note that the parameters of netconsole targets that were specified/created
-from the boot/module option are not exposed via this interface, and hence
-cannot be modified dynamically. ]
-
-To include this feature, select CONFIG_NETCONSOLE_DYNAMIC when building the
-netconsole module (or kernel, if netconsole is built-in).
-
-Some examples follow (where configfs is mounted at the /sys/kernel/config
-mountpoint).
-
-To add a remote logging target (target names can be arbitrary):
-
- cd /sys/kernel/config/netconsole/
- mkdir target1
-
-Note that newly created targets have default parameter values (as mentioned
-above) and are disabled by default -- they must first be enabled by writing
-"1" to the "enabled" attribute (usually after setting parameters accordingly)
-as described below.
-
-To remove a target:
-
- rmdir /sys/kernel/config/netconsole/othertarget/
-
-The interface exposes these parameters of a netconsole target to userspace:
-
- enabled Is this target currently enabled? (read-write)
- dev_name Local network interface name (read-write)
- local_port Source UDP port to use (read-write)
- remote_port Remote agent's UDP port (read-write)
- local_ip Source IP address to use (read-write)
- remote_ip Remote agent's IP address (read-write)
- local_mac Local interface's MAC address (read-only)
- remote_mac Remote agent's MAC address (read-write)
-
-The "enabled" attribute is also used to control whether the parameters of
-a target can be updated or not -- you can modify the parameters of only
-disabled targets (i.e. if "enabled" is 0).
-
-To update a target's parameters:
-
- cat enabled # check if enabled is 1
- echo 0 > enabled # disable the target (if required)
- echo eth2 > dev_name # set local interface
- echo 10.0.0.4 > remote_ip # update some parameter
- echo cb:a9:87:65:43:21 > remote_mac # update more parameters
- echo 1 > enabled # enable target again
-
-You can also update the local interface dynamically. This is especially
-useful if you want to use interfaces that have newly come up (and may not
-have existed when netconsole was loaded / initialized).
-
-Miscellaneous notes:
-====================
-
-WARNING: the default target ethernet setting uses the broadcast
-ethernet address to send packets, which can cause increased load on
-other systems on the same ethernet segment.
-
-TIP: some LAN switches may be configured to suppress ethernet broadcasts
-so it is advised to explicitly specify the remote agents' MAC addresses
-from the config parameters passed to netconsole.
-
-TIP: to find out the MAC address of, say, 10.0.0.2, you may try using:
-
- ping -c 1 10.0.0.2 ; /sbin/arp -n | grep 10.0.0.2
-
-TIP: in case the remote logging agent is on a separate LAN subnet than
-the sender, it is suggested to try specifying the MAC address of the
-default gateway (you may use /sbin/route -n to find it out) as the
-remote MAC address instead.
-
-NOTE: the network device (eth1 in the above case) can run any kind
-of other network traffic, netconsole is not intrusive. Netconsole
-might cause slight delays in other traffic if the volume of kernel
-messages is high, but should have no other impact.
-
-NOTE: if you find that the remote logging agent is not receiving or
-printing all messages from the sender, it is likely that you have set
-the "console_loglevel" parameter (on the sender) to only send high
-priority messages to the console. You can change this at runtime using:
-
- dmesg -n 8
-
-or by specifying "debug" on the kernel command line at boot, to send
-all kernel messages to the console. A specific value for this parameter
-can also be set using the "loglevel" kernel boot option. See the
-dmesg(8) man page and Documentation/kernel-parameters.txt for details.
-
-Netconsole was designed to be as instantaneous as possible, to
-enable the logging of even the most critical kernel bugs. It works
-from IRQ contexts as well, and does not enable interrupts while
-sending packets. Due to these unique needs, configuration cannot
-be more automatic, and some fundamental limitations will remain:
-only IP networks, UDP packets and ethernet devices are supported.