+.. SPDX-License-Identifier: GPL-2.0
+
+==========
+Netconsole
+==========
+
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
+
IPv6 support by Cong Wang <xiyou.wangcong@gmail.com>, Jan 1 2013
+
Extended console support by Tejun Heo <tj@kernel.org>, May 1 2015
Please send bug reports to Matt Mackall <mpm@selenic.com>
==================================
It takes a string configuration parameter "netconsole" in the
-following format:
+following format::
netconsole=[+][src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
where
- + if present, enable extended console support
- 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)
+ + if present, enable extended console support
+ 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:
+Examples::
linux netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
- or
+or::
insmod netconsole netconsole=@/,@10.0.0.2/
- or using IPv6
+or using IPv6::
insmod netconsole netconsole=@/,@fd00:1:2:3::1/
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:
+complete string enclosed in "quotes", thusly::
modprobe netconsole netconsole="@/,@10.0.0.2/;@/eth1,6892@10.0.0.3/"
On distributions using a BSD-based netcat version (e.g. Fedora,
openSUSE and Ubuntu) the listening port must be specified without
- the -p switch:
+ the -p switch::
+
+ nc -u -l -p <port>' / 'nc -u -l <port>
+
+ or::
- 'nc -u -l -p <port>' / 'nc -u -l <port>' or
- 'netcat -u -l -p <port>' / 'netcat -u -l <port>'
+ netcat -u -l -p <port>' / 'netcat -u -l <port>
3) socat
- 'socat udp-recv:<port> -'
+::
+
+ socat udp-recv:<port> -
Dynamic reconfiguration:
========================
Some examples follow (where configfs is mounted at the /sys/kernel/config
mountpoint).
-To add a remote logging target (target names can be arbitrary):
+To add a remote logging target (target names can be arbitrary)::
cd /sys/kernel/config/netconsole/
mkdir target1
"1" to the "enabled" attribute (usually after setting parameters accordingly)
as described below.
-To remove a target:
+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)
extended Extended mode enabled (read-write)
dev_name Local network interface name (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:
+To update a target's parameters::
cat enabled # check if enabled is 1
echo 0 > enabled # disable the target (if required)
If '+' is prefixed to the configuration line or "extended" config file
is set to 1, extended console support is enabled. An example boot
-param follows.
+param follows::
linux netconsole=+4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
Log messages are transmitted with extended metadata header in the
-following format which is the same as /dev/kmsg.
+following format which is the same as /dev/kmsg::
<level>,<sequnum>,<timestamp>,<contflag>;<message text>
If a message doesn't fit in certain number of bytes (currently 1000),
the message is split into multiple fragments by netconsole. These
-fragments are transmitted with "ncfrag" header field added.
+fragments are transmitted with "ncfrag" header field added::
ncfrag=<byte-offset>/<total-bytes>
For example, assuming a lot smaller chunk size, a message "the first
-chunk, the 2nd chunk." may be split as follows.
+chunk, the 2nd chunk." may be split as follows::
6,416,1758426,-,ncfrag=0/31;the first chunk,
6,416,1758426,-,ncfrag=16/31; the 2nd chunk.
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.
+.. 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: 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::
-TIP: to find out the MAC address of, say, 10.0.0.2, you may try using:
+ 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.
- ping -c 1 10.0.0.2 ; /sbin/arp -n | grep 10.0.0.2
+.. note::
-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.
+ 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: 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::
-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:
+ 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
+ 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/admin-guide/kernel-parameters.rst for details.
+ 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/admin-guide/kernel-parameters.rst
+ for details.
Netconsole was designed to be as instantaneous as possible, to
enable the logging of even the most critical kernel bugs. It works
projects / platform / kernel / linux-rpi.git / commitdiff