Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   2) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   3) ==========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   4) Netconsole
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   5) ==========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   6) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   7) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   8) started by Ingo Molnar <mingo@redhat.com>, 2001.09.17
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   9) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  10) 2.6 port and netpoll api by Matt Mackall <mpm@selenic.com>, Sep 9 2003
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  11) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  12) IPv6 support by Cong Wang <xiyou.wangcong@gmail.com>, Jan 1 2013
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  14) Extended console support by Tejun Heo <tj@kernel.org>, May 1 2015
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  15) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  16) Please send bug reports to Matt Mackall <mpm@selenic.com>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  17) Satyam Sharma <satyam.sharma@gmail.com>, and Cong Wang <xiyou.wangcong@gmail.com>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  18) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  19) Introduction:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  20) =============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  22) This module logs kernel printk messages over UDP allowing debugging of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  23) problem where disk logging fails and serial consoles are impractical.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  24) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  25) It can be used either built-in or as a module. As a built-in,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  26) netconsole initializes immediately after NIC cards and will bring up
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  27) the specified interface as soon as possible. While this doesn't allow
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  28) capture of early kernel panics, it does capture most of the boot
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  29) process.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  30) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  31) Sender and receiver configuration:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  32) ==================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  33) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  34) It takes a string configuration parameter "netconsole" in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  35) following format::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  36) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  37)  netconsole=[+][src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  38) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  39)    where
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  40) 	+             if present, enable extended console support
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  41) 	src-port      source for UDP packets (defaults to 6665)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  42) 	src-ip        source IP to use (interface address)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  43) 	dev           network interface (eth0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  44) 	tgt-port      port for logging agent (6666)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  45) 	tgt-ip        IP address for logging agent
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  46) 	tgt-macaddr   ethernet MAC address for logging agent (broadcast)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  47) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  48) Examples::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  49) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  50)  linux netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  51) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  52) or::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  53) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  54)  insmod netconsole netconsole=@/,@10.0.0.2/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  55) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  56) or using IPv6::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  57) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  58)  insmod netconsole netconsole=@/,@fd00:1:2:3::1/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  59) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  60) It also supports logging to multiple remote agents by specifying
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  61) parameters for the multiple agents separated by semicolons and the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  62) complete string enclosed in "quotes", thusly::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  63) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  64)  modprobe netconsole netconsole="@/,@10.0.0.2/;@/eth1,6892@10.0.0.3/"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  65) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  66) Built-in netconsole starts immediately after the TCP stack is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  67) initialized and attempts to bring up the supplied dev at the supplied
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  68) address.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  69) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  70) The remote host has several options to receive the kernel messages,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  71) for example:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  72) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  73) 1) syslogd
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  74) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  75) 2) netcat
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  76) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  77)    On distributions using a BSD-based netcat version (e.g. Fedora,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  78)    openSUSE and Ubuntu) the listening port must be specified without
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  79)    the -p switch::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  80) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  81) 	nc -u -l -p <port>' / 'nc -u -l <port>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  82) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  83)     or::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  84) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  85) 	netcat -u -l -p <port>' / 'netcat -u -l <port>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  86) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  87) 3) socat
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  88) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  89) ::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  90) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  91)    socat udp-recv:<port> -
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  92) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  93) Dynamic reconfiguration:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  94) ========================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  95) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  96) Dynamic reconfigurability is a useful addition to netconsole that enables
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  97) remote logging targets to be dynamically added, removed, or have their
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  98) parameters reconfigured at runtime from a configfs-based userspace interface.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  99) [ Note that the parameters of netconsole targets that were specified/created
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) from the boot/module option are not exposed via this interface, and hence
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) cannot be modified dynamically. ]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) To include this feature, select CONFIG_NETCONSOLE_DYNAMIC when building the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) netconsole module (or kernel, if netconsole is built-in).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) Some examples follow (where configfs is mounted at the /sys/kernel/config
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) mountpoint).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) To add a remote logging target (target names can be arbitrary)::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111)  cd /sys/kernel/config/netconsole/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112)  mkdir target1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) Note that newly created targets have default parameter values (as mentioned
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) above) and are disabled by default -- they must first be enabled by writing
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) "1" to the "enabled" attribute (usually after setting parameters accordingly)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) as described below.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) To remove a target::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)  rmdir /sys/kernel/config/netconsole/othertarget/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) The interface exposes these parameters of a netconsole target to userspace:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) 	==============  =================================       ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) 	enabled		Is this target currently enabled?	(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) 	extended	Extended mode enabled			(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) 	dev_name	Local network interface name		(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) 	local_port	Source UDP port to use			(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) 	remote_port	Remote agent's UDP port			(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) 	local_ip	Source IP address to use		(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) 	remote_ip	Remote agent's IP address		(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) 	local_mac	Local interface's MAC address		(read-only)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) 	remote_mac	Remote agent's MAC address		(read-write)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) 	==============  =================================       ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) The "enabled" attribute is also used to control whether the parameters of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) a target can be updated or not -- you can modify the parameters of only
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) disabled targets (i.e. if "enabled" is 0).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) To update a target's parameters::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143)  cat enabled				# check if enabled is 1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144)  echo 0 > enabled			# disable the target (if required)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145)  echo eth2 > dev_name			# set local interface
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146)  echo 10.0.0.4 > remote_ip		# update some parameter
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147)  echo cb:a9:87:65:43:21 > remote_mac	# update more parameters
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148)  echo 1 > enabled			# enable target again
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) You can also update the local interface dynamically. This is especially
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) useful if you want to use interfaces that have newly come up (and may not
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) have existed when netconsole was loaded / initialized).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) Extended console:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) =================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) If '+' is prefixed to the configuration line or "extended" config file
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) is set to 1, extended console support is enabled. An example boot
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) param follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161)  linux netconsole=+4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) Log messages are transmitted with extended metadata header in the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) following format which is the same as /dev/kmsg::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166)  <level>,<sequnum>,<timestamp>,<contflag>;<message text>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) Non printable characters in <message text> are escaped using "\xff"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) notation. If the message contains optional dictionary, verbatim
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) newline is used as the delimeter.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) If a message doesn't fit in certain number of bytes (currently 1000),
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) the message is split into multiple fragments by netconsole. These
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) fragments are transmitted with "ncfrag" header field added::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176)  ncfrag=<byte-offset>/<total-bytes>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) For example, assuming a lot smaller chunk size, a message "the first
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) chunk, the 2nd chunk." may be split as follows::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181)  6,416,1758426,-,ncfrag=0/31;the first chunk,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182)  6,416,1758426,-,ncfrag=16/31; the 2nd chunk.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) Miscellaneous notes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) ====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) .. Warning::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189)    the default target ethernet setting uses the broadcast
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190)    ethernet address to send packets, which can cause increased load on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191)    other systems on the same ethernet segment.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) .. Tip::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195)    some LAN switches may be configured to suppress ethernet broadcasts
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196)    so it is advised to explicitly specify the remote agents' MAC addresses
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197)    from the config parameters passed to netconsole.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) .. Tip::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201)    to find out the MAC address of, say, 10.0.0.2, you may try using::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) 	ping -c 1 10.0.0.2 ; /sbin/arp -n | grep 10.0.0.2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) .. Tip::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207)    in case the remote logging agent is on a separate LAN subnet than
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208)    the sender, it is suggested to try specifying the MAC address of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209)    default gateway (you may use /sbin/route -n to find it out) as the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210)    remote MAC address instead.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) .. note::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214)    the network device (eth1 in the above case) can run any kind
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215)    of other network traffic, netconsole is not intrusive. Netconsole
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216)    might cause slight delays in other traffic if the volume of kernel
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217)    messages is high, but should have no other impact.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) .. note::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221)    if you find that the remote logging agent is not receiving or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222)    printing all messages from the sender, it is likely that you have set
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223)    the "console_loglevel" parameter (on the sender) to only send high
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224)    priority messages to the console. You can change this at runtime using::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) 	dmesg -n 8
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228)    or by specifying "debug" on the kernel command line at boot, to send
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229)    all kernel messages to the console. A specific value for this parameter
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230)    can also be set using the "loglevel" kernel boot option. See the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231)    dmesg(8) man page and Documentation/admin-guide/kernel-parameters.rst
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232)    for details.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) Netconsole was designed to be as instantaneous as possible, to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) enable the logging of even the most critical kernel bugs. It works
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) from IRQ contexts as well, and does not enable interrupts while
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237) sending packets. Due to these unique needs, configuration cannot
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238) be more automatic, and some fundamental limitations will remain:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) only IP networks, UDP packets and ethernet devices are supported.