[systemd-devel] systemd-logger and external syslog daemon

[Lennart Poettering]

On Thu, 17.03.11 08:38, Rainer Gerhards (rgerhards at hq.adiscon.com) wrote:

> > You mean a new udev/dracut/systemd on an old kernel? The messages they
> > print would look a bit weird if they are used together with log msg
> > timestamping the way the kernel does it, since the kernel doesn't
> > recognize the prefix. (See Kay's post about this). But besides these
> > cosmetic issues nothing should really go wrong.
> > 
> > (I wonder if we can find a nice way to detect whether the kernel is new
> > enough for this, so that we could strip the facility automatically for
> > older ones. Explcitily checking for kernel versions at runtime is evil
> > though... I can't think of a good way though...)
> 
> Wouldn't it work to check if there is a "<PRI>" right at the start of the
> message? I think that it is actual user data would be extremely improbable,
> so this should be a good enough indication. That way, we could pull the PRI
> even without the kernel patch (but, granted, it is kind of an interface
> change...).

Hmm?

The question is how we can detect whether it is safe to write messages
to kmsg with PRI values with more than 3 bits. 2.6.39 and above will be able
to handle that properly, even if you enable per-line printk kernel
timestamping. On 2.6.38 only 3-bit-PRI values will look good if you use
printk kernel timestamping.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.