[systemd-devel] Question regarding configuration of SystemMaxUse and SystemKeepFree

[PureLinux Betriebsführung]

Hi,
thanks for your fast response, Andrei! It seems like i was a bit unclear 
with my explanation, so we misunderstood. Sorry for that.

I meant the actual size of the filesystem, which differs from e.g. 100M 
on a small SoC up to ~8G on a bigger server system. Not a specific 
service, which is creating too much log entries, which i need to cap.

The problem is, that due to that differences between all machines, it 
doesnt make much sense to set the same absolute value on all machines. I 
may need to say, that i am not configuring all that machines by hand - i 
am managing all that machines with Ansible and i am trying to configure 
them as homogeneous as possible.

Actually, i want to set a relative value for SystemMaxUse and/or 
SystemKeepFree in the journald configuration. So saying for example - no 
matter how much space the filesystem behind /var/log provides, you can 
use up to 60% of it.

The documentation states, that there are relative values used per 
default, but they are capped (as you mentioned) at a specific value. So 
for me, it looks like journald is also supporting relative values.

So i am wondering about the fact, that journald.conf is allowing only 
absolute values like e.g. SystemMaxUse=1G and not SystemMaxUse=60%.

I am actually unsure, whether journald is really not supporting relative 
values for the mentioned configuration directives, or whether i am just 
configuring it wrong?


Best regards
Karl

Am 02.09.23 um 07:17 schrieb Andrei Borzenkov:
> On 02.09.2023 00:29, PureLinux Betriebsführung wrote:
>> Hi,
>> i am running a bunch of partly very different systems with Debian
>> Bookworm. On this machines, i am using systemd 252 (252.12-1~deb12u1).
>>
>> If i am configuring journald, i am facing the problem, that /var/log is
>> having a very different size on all my machines. From 100M to 8G or
>> something.
>>
> 
> Documentation states that te default limit is capped at 4G. If you 
> really have 8G of journal files, you probably need to investigate why.
> 
>> Journald states, that the configuration options SystemMaxUse and
>> SystemKeepFree cannot be a relative, percentual value. But they are
>> percentual values by default.
>>
>> If i want to set a percentual value, journald only returns
>> "/etc/systemd/journald.conf:25: Failed to parse size value, ignoring: 
>> 20%"
>>
>> So my question is - is there any option to set a relative value/a
>> percentage for that values? 
> 
> Pragmatic answer - service that creates drop-in for journald.conf. It 
> can run every time and drop into /run or just once and drop into /etc.
> 
>> Per default, it seems to be possible. So why
>> not a user defined percentage?
>>
> 
> 
> 
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