[systemd-devel] systemd and netconsole

[don fisher]

I am running opensuse 42.3 with a 4.18.7 kernel. Below is my setup.
First the kernel command line:

linux 
netconsole=64001 at 192.168.7.60/eth0,64001 at 192.168.7.55/34:e6:d7:01:2a:dd 
loglevel=8

and then my receiving script:

sudo nc -v -u -l 64001 | tee netconsole.log

In summary, netconsole works fine, up to a point where it hangs at 
around 12us after boot.  Before the hang the destination output matches 
that presented by dmesg. I also looked using journalctl and find that 
there are many systemd messages, I guess as expected. The netconsole 
output terminates after systemd messages. The last message transmitted 
by netconsole is:

  kernel: NFSD: starting 90-second grace period (net f00000a8)

It is hard to estimate now many systemd messages are in the journal 
because there are "Journal stopped" messages where I assume there is a 
data overrun error. But there are many.

It appears that netconsole works well maybe until systemd starts 
logging. I think I read in "Rethinking PID 1" that systemd sets up 
logging, I assume by connecting to printk. Can you help me with this 
connection? I also see systemd messages about setting up vconsole, but 
do not know if there is a conflict. I do not know what code systemd uses 
to connect to printk, or what it should try and do. netconsole connects 
to printk with a "register_console (&netconsole_ext)". Is this 
connection possibly broken by the systemd startup? I search the kernel 
list and find that may people are using netconsole, so I am confident 
there is a way to make it work.

Please advise if you have any ideas on how to proceed. I can post log 
files if there is space. I am also willing to run any experiments.

Thanks. I have tried many lists including kernel and newbie-kernel, and 
have received no response.

Don