[systemd-devel] Need clarity on journald.conf options

[Amish]

Hello,

I am trying to seek clarity on few of journald.conf options.

This is what I have set in journald.conf.d/99-local.conf

[Journal]
# allocate maximum 100GB for all journal files combined
SystemMaxUse=100G

# But keep atleast 15% of disk space; free.
# no value specified - for default (i.e. 15%)
SystemKeepFree=

# Maximum size of one journal file should not exceed 200MB.
SystemMaxFileSize=200M

# But rotate it every week (even if size is less than 200MB)
MaxFileSec=1week

# No limit on number of journal files created (see query below)
SystemMaxFiles=0

# Keep files for 3 years. (unless MaxUse/KeepFree is crossed)
MaxRetentionSec=3year


Please let me know if settings are correct (as mentioned in annotation)

I am confused about SystemMaxUse documentation which says "each value is 
capped to 4G". Does it mean that 4G is maximum I can set? i.e. maximum 
space that all journal files combined will be 4G even if I set it to 100G?

I am also confused about SystemMaxFiles=0, as documentation states that 
100 is default. So does setting it to ZERO set it to default i.e. 100 or 
it sets to unlimited?

I do not want files to vanish after 2 years i.e. after 104 rotations. 
Documentation does not state how to set it to unlimited. i.e.
SystemMaxFiles= (should mean default i.e. 100)
SystemMaxFiles=0 (should mean unlimited and not 100)

I can set it to very high value though to avoid any confution.

May be documentation needs to be little more clear?

Please guide,

Thank you

Amish.