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Message-Id: <20070704110819.28520.50445.sendpatchset@cselinux1.cse.iitk.ac.in> Date: Wed, 04 Jul 2007 16:38:19 +0530 From: Satyam Sharma <ssatyam@....iitk.ac.in> To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Cc: Keiichi Kii <k-keiichi@...jp.nec.com>, Satyam Sharma <ssatyam@....iitk.ac.in>, Netdev <netdev@...r.kernel.org>, Joel Becker <joel.becker@...cle.com>, Matt Mackall <mpm@...enic.com>, Andrew Morton <akpm@...ux-foundation.org>, David Miller <davem@...emloft.net> Subject: [PATCH -mm 8/9] netconsole: Update documentation for dynamic reconfigurability From: Satyam Sharma <ssatyam@....iitk.ac.in> [8/9] netconsole: Update documentation for dynamic reconfigurability Add myself to parties interested in receiving bug reports, and give lots of examples. Also fix some whitespace inconsistencies I introduced earlier. Signed-off-by: Satyam Sharma <ssatyam@....iitk.ac.in> Cc: Keiichi Kii <k-keiichi@...jp.nec.com> Cc: Takayoshi Kochi <t-kochi@...jp.nec.com> --- Documentation/networking/netconsole.txt | 70 +++++++++++++++++++++++++++++++- 1 file changed, 68 insertions(+), 2 deletions(-) --- diff -ruNp a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt --- a/Documentation/networking/netconsole.txt 2007-07-04 03:12:25.000000000 +0530 +++ b/Documentation/networking/netconsole.txt 2007-07-04 12:24:44.000000000 +0530 @@ -3,6 +3,10 @@ started by Ingo Molnar <mingo@...hat.com 2.6 port and netpoll api by Matt Mackall <mpm@...enic.com>, Sep 9 2003 Please send bug reports to Matt Mackall <mpm@...enic.com> +and Satyam Sharma <satyam.sharma@...il.com> + +Introduction: +============= This module logs kernel printk messages over UDP allowing debugging of problem where disk logging fails and serial consoles are impractical. @@ -13,6 +17,9 @@ the specified interface as soon as possi 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: @@ -38,7 +45,7 @@ It also supports logging to multiple rem 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@...0.0.3/" + modprobe netconsole netconsole="@/,@10.0.0.2/;@/eth1,6892@...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 @@ -46,6 +53,64 @@ address. The remote host can run either 'netcat -u -l -p <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. + +To include this feature, select CONFIG_NETCONSOLE_DYNAMIC when building the +netconsole module (or kernel, if netconsole is built-in). + +Some examples follow (configfs is mounted at the /config mountpoint, say). + +To add a remote logging target (target names can be arbitrary): + + cd /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 /config/netconsole/othertarget/ + +The interface exposes these parameters of a netconsole target to userspace: + + id Unique identifier for this target (read-only) + enabled Is this target currently enabled? (read-write) + dev_name Local network interface name (read-only) + local_ip Source IP address to use (read-write) + remote_ip Remote agent's IP address (read-write) + local_port Source UDP port to use (read-write) + remote_port Remote agent's UDP port (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 + +Note that you can even update the local interface dynamically. This is +especially useful if you want to use interfaces that have newly come up +and didn't even exist 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. @@ -55,7 +120,8 @@ so it is advised to explicitly specify t from the config parameters passed to netconsole. TIP: to find out the MAC address of 10.0.0.2, you may try using: -ping -c 1 10.0.0.2 ; /sbin/arp -n | grep 10.0.0.2 + + 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 default gateway's - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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