blob: 53618fb1a717d6e5a1807118520857c2c7dc6748 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001
2started by Ingo Molnar <mingo@redhat.com>, 2001.09.17
32.6 port and netpoll api by Matt Mackall <mpm@selenic.com>, Sep 9 2003
4
5Please send bug reports to Matt Mackall <mpm@selenic.com>
6
7This module logs kernel printk messages over UDP allowing debugging of
8problem where disk logging fails and serial consoles are impractical.
9
10It can be used either built-in or as a module. As a built-in,
11netconsole initializes immediately after NIC cards and will bring up
12the specified interface as soon as possible. While this doesn't allow
13capture of early kernel panics, it does capture most of the boot
14process.
15
16It takes a string configuration parameter "netconsole" in the
17following format:
18
19 netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
20
21 where
22 src-port source for UDP packets (defaults to 6665)
23 src-ip source IP to use (interface address)
24 dev network interface (eth0)
25 tgt-port port for logging agent (6666)
26 tgt-ip IP address for logging agent
27 tgt-macaddr ethernet MAC address for logging agent (broadcast)
28
29Examples:
30
31 linux netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
32
33 or
34
35 insmod netconsole netconsole=@/,@10.0.0.2/
36
37Built-in netconsole starts immediately after the TCP stack is
38initialized and attempts to bring up the supplied dev at the supplied
39address.
40
41The remote host can run either 'netcat -u -l -p <port>' or syslogd.
42
43WARNING: the default target ethernet setting uses the broadcast
44ethernet address to send packets, which can cause increased load on
45other systems on the same ethernet segment.
46
47NOTE: the network device (eth1 in the above case) can run any kind
48of other network traffic, netconsole is not intrusive. Netconsole
49might cause slight delays in other traffic if the volume of kernel
50messages is high, but should have no other impact.
51
52Netconsole was designed to be as instantaneous as possible, to
53enable the logging of even the most critical kernel bugs. It works
54from IRQ contexts as well, and does not enable interrupts while
55sending packets. Due to these unique needs, configuration can not
56be more automatic, and some fundamental limitations will remain:
57only IP networks, UDP packets and ethernet devices are supported.