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| − | In case you are experiencing a kernel crash ([[oops]]) and have already [[Hardware testing|tested your hardware]], you should report what kernel says to the console (i.e. an [[oops]] text) to [https://bugs.openvz.org/ bug tracker]. Sometimes kernel crashes so badly that <tt>syslogd</tt> is not working and what kernel says is never written to a file. If this is the case, you have to catch what kernel says. There are several ways possible. | + | In case you are experiencing a kernel crash (oops) and have already [[Troubleshooting:Hardware|checked your hardware]], you should report what kernel says to the console to [http://bugzilla.openvz.org/ Bugzilla]. Sometimes kernel crashes so badly that syslogd is not working and what kernel says it never written to a file. If this is the case, you have to catch what kernel says. There are several ways possible. |
| − | | |
| − | == KDump ==
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| − | | |
| − | With RHEL6-based servers, kdump is pre-configured. See http://kb.odin.com/en/10044 to check the configuration. Dumps can be found under <code>/var/crash/</code> directory.
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| | == Manual/Photo == | | == Manual/Photo == |
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| | == Serial console == | | == Serial console == |
| − | Here is a description of a common routine that is necessary to set up a serial console.
| + | FIXME |
| − | | |
| − | === Hardware setup ===
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| − | First of all you should make sure that your node has a [[w:Serial port|serial port]]. If there is no such port then
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| − | unfortunately this way is not for you.
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| − | | |
| − | Then you need to find a second machine with a serial port on it.
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| − | This machine will be used to collect logs from your primary machine. Further you need to acquire
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| − | so-called [[w:Serial cable|null modem cable (a.k.a. serial cable)]] and it must be long enough to connect these two machines.
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| − | | |
| − | === Software setup ===
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| − | | |
| − | ==== Sending side ====
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| − | In your boot loader add the following kernel parameters:
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| − | <pre>
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| − | console=ttyS0,115200 console=tty0
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| − | </pre>
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| − | | |
| − | <!--T:10-->
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| − | {{Warning|make sure kernel command line does '''not''' contain the word '''<code>quiet</code>''', otherwise most of the kernel messages will not be printed to console.}}
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| − | | |
| − | <!--T:11-->
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| − | For example, in GRUB boot loader configuration file <tt>/boot/grub/grub.conf</tt> it looks like this:
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| − | <pre>
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| − | title Fedora Core (2.6.16-026test014.1-smp)
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| − | root (hd0,0)
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| − | kernel /vmlinuz-2.6.16-026test014.1-smp ro root=LABEL=/ console=ttyS0,115200 console=tty debug silencelevel=8
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| − | initrd /initrd-2.6.16-026test014.1-smp.img
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| − | </pre>
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| − | | |
| − | Kernel loaded with such parameters will send all kernel messages to /dev/ttyS0 (first serial port, a.k.a. COM1). If you have several ports, make sure that your null modem cable is connected to the appropriate port.
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| − | | |
| − | ==== Receiving side ==== <!--T:13-->
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| − | On the second node you should run any software that can log from /dev/ttyS0.
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| − | | |
| − | <!--T:14-->
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| − | It can be usual
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| − | <pre>
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| − | cat /dev/ttyS0 > /var/log/serial.log &
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| − | </pre>
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| − | or something more sophisticated: syslogd, watchtty etc.
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| − | | |
| − | ==== Port setup ====
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| − | One more important thing. 115200 in the example above is the rate of emitting port. Receiving port must also work at the same rate. For example, to tune ttyS0 rate use stty program like this:
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| − | <pre>
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| − | stty 115200 < /dev/ttyS0
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| − | </pre>
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| − | | |
| − | Some other serial port parameters, like parity, number of stop bits etc. should also be the same on both sides.
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| | | | |
| | == Netconsole == | | == Netconsole == |
| | | | |
| − | === Kernel recompilation ===
| + | This assumes you have not yet compiled netconsole as a module or into your kernel. |
| − | If you use binary kernel from openvz.org, it already has netconsole module compiled in, so just skip to next section.
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| − | | |
| − | If you build the kernel yourself, you might need to check if netconsole is compiled. To that effect, change to your kernel source directory and grep your kernel <tt>.config</tt> for NETCONSOLE:
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| − | <pre>
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| − | # cd /usr/src/openvz/linux-2.6.16
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| − | # grep NETCONSOLE .config
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| − | </pre>
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| − | | |
| − | If you see nothing or "# CONFIG_NETCONSOLE is not set" you need to recompile the kernel.
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| | | | |
| − | Edit your kernel configuration file <tt>.config</tt> with a text editor (<tt>nano .config</tt> or <tt>vi .config</tt>). Set netconsole to Y or M (depending on whether you want it as a module or built into the kernel; I have compiled it as a module): | + | Edit your kernel configuration file, in my case mine was located at /usr/src/openvz/linux-2.6.16 |
| | + | edit .config with a text editor (nano .config) |
| | + | set netconsole to Y or M (depending on whether you want it as a module or built into the kernel, i installed it as a module) |
| | | | |
| | <pre>CONFIG_NETCONSOLE=m</pre> | | <pre>CONFIG_NETCONSOLE=m</pre> |
| | | | |
| − | Save the file, then recompile the kernel:
| + | save then recompile the kernel. |
| − | | + | cd /usr/src/openvz/linux-2.6.16 |
| − | # make bzImage && make modules && make modules_install
| + | make bzImage && make modules && make modules_install |
| − | | + | update your bootloader for the new updated kernel. in my case i use lilo so i just type lilo at the prompt. |
| − | Update your bootloader for the new updated kernel. In my case I use LILO so I just type lilo at the prompt.
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| − | | |
| − | Reboot into new kernel.
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| − | | |
| − | === Setting up OpenVZ side ===
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| − | | |
| − | Next you want your netconsole to send the request to somewhere. Load netconsole module, specifying the remote server parameters:
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| − | | |
| − | # modprobe netconsole netconsole=4444@10.0.2.1/eth0,6666@10.0.2.2/00:05:5D:34:11:AF
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| − | | |
| − | This will load the module with your settings. Replace your local IP address with where <tt>10.0.2.1</tt> is, <tt>eth0</tt> with your network interface card device, <tt>6666</tt> with the remote netconsole port (UDP), and <tt>10.0.2.2</tt> with your remote netconsole server IP. Also add in the mac address of your remote netconsole server, which in my case was 00:05:5D:34:11:AF. You can get the MAC address using arp utility:
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| − | | |
| − | <pre>
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| − | # ping -c 1 10.0.2.2
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| − | # /sbin/arp -n 10.0.2.2
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| − | Address HWtype HWaddress Flags Mask Iface
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| − | 10.0.2.2 ether 00:05:5D:34:11:AF C eth0
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| − | </pre>
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| − | | |
| − | If the remote netconsole server is outside of local network area, use mac address of default gateway or router on local network area and IP address of remote netconsole server (loging via WAN). Mac address of default gateway or router you can get the same way (ping to gateway/router and see mac address via arp command).
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| − | | |
| − | Netconsole documentation is available from <tt>Documentation/networking/netconsole.txt</tt> file under your kernel source directory.
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| − | | |
| − | === Setting from initrd ===
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| − | | |
| − | To log the boot process before root filesystem is mounted, network device driver and netconsole modules must be loaded from initd.
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| − | | |
| − | | |
| − | RedHat 5/CentOS 5:
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| − | echo 'MODULES+="<network-driver-module> netconsole "' > /etc/sysconfig/mkinitrd/netconsole
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| − | chmod +x /etc/sysconfig/mkinitrd/netconsole
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| − | echo 'options netconsole netconsole=<sport>@<saddr>/<dev>,<dport>@<daddr>/<dmac>' >> /etc/modprobe.conf
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| − | | |
| − | Debian/Ubuntu:
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| − | echo '<network-driver-module>' >> /etc/initramfs-tools/modules
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| − | echo 'netconsole netconsole=<sport>@<saddr>/<dev>,<dport>@<daddr>/<dmac>' >> /etc/initramfs-tools/modules
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| − | | |
| − | and rebuild initrd.
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| − | | |
| − | === Setting up rsyslogd ===
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| − | | |
| − | | |
| − | /etc/rsyslog.d/netconsole.conf
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| − | | |
| − | $template NetconsoleFile,"/var/log/netconsole/%FROMHOST%-%$NOW%.log"
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| − | $template NetconsoleFormat,"%rawmsg%"
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| − |
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| − | $EscapeControlCharactersOnReceive off
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| − | $DropTrailingLFOnReception off
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| − | $RepeatedMsgReduction off
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| − |
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| − | $RuleSet NetconsoleRuleset
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| − | *.* ?NetconsoleFile;NetconsoleFormat
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| − | $RuleSet RSYSLOG_DefaultRuleset
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| − |
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| − | $ModLoad imudp
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| − | $InputUDPServerBindRuleset NetconsoleRuleset
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| − | $UDPServerRun 6666
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| − | | |
| − | === Setting up remote side ===
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| − | | |
| − | Set up '''netcat''' ('''nc''' on some Linux distributions) on your console server to listen on port 6666 UDP:
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| − | | |
| − | netcat -u -l -p6666
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| − | | |
| − | or
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| − | | |
| − | nc -lu 6666
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| − | | |
| − | or
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| − | | |
| − | socat udp-listen:6666,reuseaddr -
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| − | | |
| − | When your kernel prints something on the console, the text will be also captured on this netconsole server.
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| − | | |
| − | ==== Adding to inittab ====
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| − | For automatic care about capturing on console server you can use init respawn feature in this way:
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| − | | |
| − | echo "n1:23:respawn:/bin/netcat -u -l -p 6666 >> /var/log/netconsole" >> /etc/inittab
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| − | telinit q
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| − | | |
| − | ==== Adding date/time to messages ====
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| − | | |
| − | If you want the log to contain date/time of each line, you can use '''awk''' like this:
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| − | | |
| − | netcat -u -l -p6666 | awk '{print strftime("%d %b %Y %H:%M:%S"), $0; fflush(stdout);}' >> /var/log/netconsole
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| − | | |
| − | See man strftime for info about how to tailor strftime() argument to your needs.
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| − | | |
| − | Note that if you want to add this to /etc/inittab, it should be done like this:
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| − | | |
| − | echo "netcat -u -l -p6666 | awk '{print \
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| − | strftime("%d %b %Y %H:%M:%S"), \$0; fflush(stdout);}' \
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| − | >> /var/log/netconsole" > /usr/local/sbin/netconsole
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| − | chmod a+x /usr/local/sbin/netconsole
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| − | echo "n1:23:respawn:/usr/local/sbin/netconsole" >> /etc/inittab
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| − | telinit q
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| − | | |
| − | ==== Configuring logrotate ====
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| − | | |
| − | For long term capturing you would like to do log rotating some way. With logrotate you can do it by creating config file /etc/logrotate.d/netconsole:
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| − | | |
| − | <pre>
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| − | /var/log/netconsole {
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| − | weekly
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| − | rotate 8
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| − | missingok
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| − | compress
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| − | copytruncate
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| − | notifempty
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| − | # Need to restart logger after log file move
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| − | postrotate
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| − | # Below line assumes netcat will be restarted by init
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| − | killall -TERM netcat > /dev/null 2>&1 || true
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| − | }
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| − | </pre>
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| − | | |
| − | <!--T:53-->
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| − | For more details, see man logrotate.
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| − | | |
| − | === Testing netconsole ===
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| − | First, check log level of console messages on OpenVZ side by:
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| − | | |
| − | cat /proc/sys/kernel/printk
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| − | | |
| − | First number should be 7 for testing. You can arrange it by:
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| − | | |
| − | sysctl -w kernel.printk="7 4 1 7"
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| | | | |
| − | After testing you can restore previous setting the same way.
| + | next you want your netconsole to send the request to somewhere. |
| | | | |
| − | Load '''netconsole''' module (see above) and on the console server run netcat (nc) command. On OpenVZ side provoke any console message, for example connect any USB hardware or try command:
| + | <pre>modprobe netconsole netconsole=4444@10.0.2.2/eth0,6666@10.0.2.1/00:05:5D:34:11:AF</pre> |
| | | | |
| − | modprobe tun
| + | this will load the module in with your settings. replace your ip address with where 10.0.2.2 is, eth0 is your network interface card. 6666 is the remote netconsole port (UDP), and replace 10.0.2.1 with your remote netconsole server. also add in the mac address of your netconsole server, which in my case was 00:05:5D:34:11:AF. |
| | | | |
| − | If you see any console message on OpenVZ side, you should see message on console server too. If not, something is wrong. When debugging a problem, do not use tcpdump on OpenVZ side — it is not able to show netconsole packets. Instead, use tcpdump on console server. Quite a common source of problems with netconsole are firewalls.
| + | then just setup netcat on your console server to listen on port 6666 UDP. |
| | | | |
| − | == See also ==
| + | <pre>netcat -u -l -p6666</pre> |
| − | * [[SysRq debugger]]
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| − | * [[Kernel debug options]]
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| | | | |
| − | == External links ==
| + | when your openvz kernel performs an OOPS, it will be captured on the netconsole server :) |
| − | * [http://kb.odin.com/en/10044 How to configure kdump (kernel crash dump)]
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| | | | |
| − | [[Category:QA]]
| + | enjoy. |
| − | [[Category:HOWTO]]
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| − | [[Category:Kernel]]
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| − | [[Category:Troubleshooting]]
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