Re: [PATCH RFC 0/2] netconsole: allow replaying the printk buffer on demand

[John Ogness <john.ogness@linutronix.de>]

On 2026-10-24, Sam Crossley <samuelcrossley@gmail.com> wrote:
> Netconsole only forwards records while an enabled target and its
> transport are available. A target enabled after boot, or one that was
> unreachable during a network outage, leaves a gap in the remote log that
> cannot currently be recovered.

This situation is no different than connecting a UART sometime after
boot, or having unplugged a serial cable temporarily during runtime.

> This adds a write-only "replay" attribute to the netconsole configfs
> subsystem that rewinds the netconsole consoles so the retained ring is
> re-sent.

I would prefer that we find a more general interface for this. One that
can apply to all consoles, not just netconsole.

We have a couple console features planned or in discussion: per-console
loglevels [0] and per-console unsafe dumping/ordering [1]. Both of these
are per-console, meaning they also involve the netconsole.

I think we need the netconsole to support a general console interface
rather than introducing netconsole-only knobs (particularly when such
features could be valid for any console).

In the per-console loglevel series Chris Down introduces [2]
/sys/class/console/ to sysfs. This is where we would put all the
upcoming per-console knobs. I would expect a replay trigger would fit
well there.

John Ogness

[0] https://lore.kernel.org/lkml/cover.1764272407.git.chris@chrisdown.name/
[1] https://lore.kernel.org/lkml/87bj8kkfwk.fsf@jogness.linutronix.de/
[2] https://lore.kernel.org/lkml/84b8d91693e56f6026271bc40553bcb6657ab24d.1764272407.git.chris@chrisdown.name/