Response to systemd's use of the debug flag

>Correct. I don't mind people piggy-backing on some fairly obvious generic term like "debug" per se. I don't know if the old init scripts did that, but I do know they did it for "quiet", which is basically the reverse of "debug".

>What I mind is people closing bugs and not admitting mistakes. If Kay had even said "sorry, the excessive output was a bug in systemd, it's already fixed in current -git", that would have been a valid reason to close the bug.

So Torvalds is saying he doesn't like dictatorial project maintainers who reply in an abrupt and abrasive manner to contributors? He is so concerned about the lack of politeness and professional discourse that he just had to raise this issue? Hilarious.

I have a fair amount of experience with Linux, but I'm a little lost by what's going on here. Can someone out there dumb this down a bit for an init newbie?

In a nutshell, a Linux kernel developer wants to limit the number of debugging messages he is obliged to read and act on, and Linus Torvalds thinks that's counterproductive, and Linus generally says what he thinks.

In a nutshell. :)

You can pass the kernel options before booting. i.e. "quiet" or "debug". The Kernel exposes these options via /proc/cmdline.

systemd parses /proc/cmdline and if "debug" is set, it also raises it's log level to debug. Then systemd logs so much to the kernel log that it gets flooded and fails to boot.

Edit: And story wise, systemd says yeah, we're not going to fix this or rename the debug flag for systemd to "systemd.debug" because blah.

And Torvalds gets pissed.

The kernel has a debug option that can be specified at boot time to increase its logging verbosity. systemd looks at the kernel command line to do the same and starts writing its own verbose logging out to the kernel's message buffer. Writing out to the kernel message buffer is done for pragmatic reasons: generally if you're debugging init problems they're happening when the machine is first starting so you would like to see the error messages on the serial console/virtual console.

The bug that started this all came up when someone had a broken system that was causing systemd to spew out tons of log messages. This was overwhelming the kernel message system and causing things to time out/etc and resulted in an unbootable system. When this problem got opened upstream, the systemd maintainer said "not my problem."

There are a couple of ways forward here: systemd can limit its own output and say "my bad"[1], systemd can begin looking for its own debug flag in the kernel command line instead of using the kernel's own debug flag or the kernel can implement rate limiting on the message system[2] to keep userspace from shooting itself in the foot.

Torvalds really doesn't like the systemd maintainer's "not my problem" attitude so he's threatened to no longer accept pull requests from him for any code he writes. Torvalds wrote a really good post in the linked Google+ comments that describes his feelings on the whole thing:

"I don't mind people piggy-backing on some fairly obvious generic term like "debug" per se. I don't know if the old init scripts did that, but I do know they did it for "quiet", which is basically the reverse of "debug".

What I mind is people closing bugs and not admitting mistakes. If Kay had even said "sorry, the excessive output was a bug in systemd, it's already fixed in current -git", that would have been a valid reason to close the bug.

And for the people thinking this is a storm in a teacup: this is not the first time Kay has done this, which is why I personally get so frustrated.

Kay has done the exact same thing with major bugs that were not fixed anywhere else, and that caused machines to fail at boot time, and Kay happily pointed the finger elsewhere for months at a time and closed bugzilla entries. 

Side explanatory note: and it's because of that known history of abusive behavior that I would prefer systemd now use "systemd.debug".

The old init scripts may or may not have parsed "debug", but we never had any reason to care. Now we do, and people are (I think) understandably upset that systemd not only screwed up, but then the people involved weren't even willing to say "sorry" about it but instead go "uh, it wasn't our bug, deal with it"."

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[1] This happened

[2] This will likely happen