[systemd-devel] Netconsole NG

Tue Apr 8 14:27:26 PDT 2014

On 08.04.2014 14:25, Tom Gundersen wrote:
> On Tue, Apr 8, 2014 at 2:10 PM, poma <pomidorabelisima at gmail.com> wrote:
>> On 08.04.2014 04:03, poma wrote:
>>> On 07.04.2014 19:55, Zbigniew Jędrzejewski-Szmek wrote:
>>>> On Mon, Apr 07, 2014 at 05:34:10PM +0200, Lukáš Nykrýn wrote:
>>>>> The reason why this was not rewritten a long time ago is that the
>>>>> initscript tries to figure some of those values by itself (for
>>>>> example the MAC address). But yes, we need to do something with
>>>>> netconsole. It is a blocker for my initscripts evil plan.
>>>> Doesn't netconsole figure out most of those settings by itself, and
>>>> others default to sensible values, so if the network card is up
>>>> and has an address configured, only the device and target ip must be given?
>>>>
>>>>> Dne 6.4.2014 17:59, poma napsal(a):
>>>>>>
>>>>>> /etc/sysconfig/netconsole:
>>>>>> # This is the EnvironmentFile for the netconsole service. Starting this
>>>>>> # service enables the capture of dmesg output on a destination machine.
>>>>>>
>>>>>> # Source port
>>>>>> SRC_PORT=12345
>>>> This should default to empty... Kernel will pick something.
>>>>
>>>>>>
>>>>>> # Source IP address
>>>>>> SRC_IP=192.168.1.2
>>>> This should default to empty... Kernel will use configured address,
>>>> since we order after network.target anyway.
>>>>
>>>>>> # Source network device
>>>>>> SRC_DEV=enp1s2
>>>> Maybe this can be made into a instance argument?
>>>>
>>>>>> # Destination port
>>>>>> DST_PORT=12345
>>>> I think this should default to 514/syslog, and can be left unset.
>>>>
>>>>>> # Destination IP address
>>>>>> DST_IP=192.168.1.1
>>>>>>
>>>>>> # Destination ethernet address
>>>>>> DST_EHA=00:11:22:33:44:55
>>>> This should default to unset. The kernel will query it if not set.
>>>>
>>>>>> /usr/lib/systemd/system/netconsole.service:
>>>>>> [Unit]
>>>>>> Description=Adds the netconsole module with the configured parameters
>>>>>> After=network.target
>>>>>>
>>>>>> [Service]
>>>>>> EnvironmentFile=/etc/sysconfig/netconsole
>>>> This is Fedora/RH specific. But I don't know what the proper path should
>>>> be, so maybe this is OK for now.
>>>>
>>>>>> Type=simple
>>>> This is the default... No need to specify.
>>>>
>>>>>> RemainAfterExit=yes
>>>>>> ExecStart=/usr/sbin/modprobe netconsole
>>>> This should be /sbin/modprobe for compatibility with split root.
>>>>
>>>>>> netconsole=${SRC_PORT}@${SRC_IP}/${SRC_DEV},${DST_PORT}@${DST_IP}/${DST_EHA}
>>>>>> ExecStop=/usr/sbin/modprobe -r netconsole
>>>> Ditto.
>>>>
>>>>>>
>>>>>> [Install]
>>>>>> WantedBy=multi-user.target
>>>> That's a really late... But I don't see a better place unfortunately.
>>>>
>>>>>> The original SysV netconsole service with related config - still in use,
>>>>>> https://git.fedorahosted.org/cgit/initscripts.git/plain/rc.d/init.d/netconsole
>>>>>> https://git.fedorahosted.org/cgit/initscripts.git/plain/sysconfig/netconsole
>>>>>>
>>>>>> Feel free to comment.
>>>> Looks like an improvement on status quo.
>>>>
>>>> Zbyszek
>>>>
>>>
>>> Shall we still leave something for users to configure.
>>> Thanks for your review.
>>>
>>
>> $ cat /usr/lib/systemd/system/netconsole-zbyszek.service
>> [Unit]
>> Description=Adds the netconsole module with the configured parameters
>> After=network.target
>>
>> [Service]
>> EnvironmentFile=/etc/sysconfig/netconsole-zbyszek
>> RemainAfterExit=yes
>> ExecStart=/sbin/modprobe netconsole netconsole=@/${SRC_DEV},@${DST_IP}/
>> ExecStop=/sbin/modprobe -r netconsole
>>
>> [Install]
>> WantedBy=multi-user.target
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> $ cat /etc/sysconfig/netconsole-zbyszek
>> # This is the EnvironmentFile for the netconsole service. Starting this
>> # service enables the capture of dmesg output on a destination machine.
>>
>> # Source network device
>> SRC_DEV=enp1s2
>>
>> # Destination IP address
>> DST_IP=192.168.1.1
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> $ dmesg | grep netcon
>> [   24.361611] netpoll: netconsole: local port 6665
>> [   24.361764] netpoll: netconsole: local IPv4 address 0.0.0.0
>> [   24.361893] netpoll: netconsole: interface 'enp1s2'
>> [   24.362061] netpoll: netconsole: remote port 6666
>> [   24.362344] netpoll: netconsole: remote IPv4 address 192.168.1.1
>> [   24.362635] netpoll: netconsole: remote ethernet address
>> ff:ff:ff:ff:ff:ff
>> [   24.362909] netpoll: netconsole: no IP address for enp1s2, aborting
>> [   24.363186] netconsole: cleaning up
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> This turns out to be a bare minimum, i.e.
>> # modprobe netconsole netconsole=@/enp1s2, at 192.168.1.1/
>> but that is also squeeze breeze ...
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> $ cat /usr/lib/systemd/system/netconsole-poma.service
>> [Unit]
>> Description=Adds the netconsole module with the configured parameters
>> After=network.target
>>
>> [Service]
>> EnvironmentFile=/etc/sysconfig/netconsole-poma
>> RemainAfterExit=yes
>> ExecStart=/sbin/modprobe netconsole
>> netconsole=@${SRC_IP}/${SRC_DEV},@${DST_IP}/
>> ExecStop=/sbin/modprobe -r netconsole
>>
>> [Install]
>> WantedBy=multi-user.target
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> $ cat /etc/sysconfig/netconsole-poma
>> # This is the EnvironmentFile for the netconsole service. Starting this
>> # service enables the capture of dmesg output on a destination machine.
>>
>> # Source IP address
>> SRC_IP=192.168.1.2
>>
>> # Source network device
>> SRC_DEV=enp1s2
>>
>> # Destination IP address
>> DST_IP=192.168.1.1
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> $ dmesg | grep netcon
>> [   23.156730] netpoll: netconsole: local port 6665
>> [   23.156735] netpoll: netconsole: local IPv4 address 192.168.1.2
>> [   23.156736] netpoll: netconsole: interface 'enp1s2'
>> [   23.156737] netpoll: netconsole: remote port 6666
>> [   23.156738] netpoll: netconsole: remote IPv4 address 192.168.1.1
>> [   23.156739] netpoll: netconsole: remote ethernet address
>> ff:ff:ff:ff:ff:ff
>> [   23.156742] netpoll: netconsole: device enp1s2 not up yet, forcing it
>> [   25.539701] console [netcon0] enabled
>> [   25.539720] netconsole: network logging started
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> And this turns out to be a true bare minimum, i.e.
>> # modprobe netconsole netconsole=@192.168.1.2/enp1s2, at 192.168.1.1/
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This looks like a definitive improvement.
> 
> Maybe one day we want to take things one step further and unify the
> logic for built-in and modular netconsole (the current way feels a bit
> odd).
> 
> Cheers,
> 
> Tom
> 

In fact, this method has long been known from the
Lm_sensors - Linux hardware monitoring
http://lm-sensors.org/browser/lm-sensors/trunk/prog/init/lm_sensors.service
[Unit]
Description=Initialize hardware monitoring sensors

[Service]
EnvironmentFile=/etc/sysconfig/lm_sensors
Type=oneshot
RemainAfterExit=yes
ExecStart=-/sbin/modprobe -qab $BUS_MODULES $HWMON_MODULES
ExecStart=/usr/bin/sensors -s
ExecStop=-/sbin/modprobe -qabr $BUS_MODULES $HWMON_MODULES

[Install]
WantedBy=multi-user.target


poma