[systemd-devel] Confusing journal information - journal size

[Lennart Poettering]

On Fri, 17.07.15 13:13, David Sommerseth (davids at redhat.com) wrote:

> 
> Hi,
> 
> I'm looking through some journals now, and even though I've seen it a
> few times I haven't thought about it until now.
> 
>    systemd-journal[1151]: Runtime journal is using 8.0M (max allowed
>              4.0G, trying to leave 4.0G free of 63.7G available →
>              current limit 4.0G).
> 
> Could this line be cleaned up so you don't have to look up a man page to
> try to figure out what this really means?  Here's my uneducated guess
> and confusion of this line:
> 
> * Runtime journal is using 8.0M
>   - Okay, so currently the journal uses 8MB of disk-space.  No problem.
> 
> * max allowed 4.0G
>   - Okay, so the journal should not grow beyond 4GB, makes sense.  No
>     problem.
> 
> * trying to leave 4.0G free of 63.7G available
>   - Uhm, what!? So it will grow until there is 4GB left on the
>     filesystem?  Not so okay.
> 
> * current limit 4.0G
>   - Ehh ... okay ... so make up your mind, please!  So will the
>     journal grow until 4GB or 59.7GB.
> 
> 
> But then I looked into /var/log/journal ...
> 
>   # du --si -s /var/log/journal/
>   4.3G	/var/log/journal/
> 
> I do see that both system,journal and user-UID.journal are both 8.4MB,
> and from that I can guess what the log entry tried to tell me with
> "Runtime journal" ... but how is /that/ information useful for me, from
> a sys-admin point of view?
> 
> My point is ... you're providing too much information and you need to
> understand more underlying things about the journal.  Simply state how
> much disk-space the journal uses now and how much it will grow.  Period.
>  Don't do any "we can grow until size X, but decided to grow to Y
> instead" information.

Well, you might not find this information useful, others however
will. These are logs, and I think it's a good idea to be rather
slightly too verbose than slightly too little verbose. Hence I think
that this information should continue to be shown. It's not pages and
pages of rubbish after all, just a single log message shown on very
few occasions. 

That siad, I have now reworded things a bit, to make this easier to
grok:

https://github.com/systemd/systemd/pull/665

With that change you'll see a message like this:

    systemd-journal[1151]: Runtime journal (/run/log/journal) is currently using 8.0M.
                           Maximum allowed usage is set to 4.0G.
                           Leaving at least 4.0G free (of currently available 63.7G disk space).
                           Enforced usage limit is thus 4.0G.

I hope this clears things up a bit. If you still find this too
confusing, send a patch, and please explain why the bikeshed looks
better in green.

Thanks,

Lennart

-- 
Lennart Poettering, Red Hat