Stop logging to deal with /var/log

I have /var/log mounted as separate partition, so trying to umount it gets to:

root@mail:~# umount /var/log
umount: /var/log: target is busy.

Let’s look what is blocking it:

lsof | grep 'var/log'
systemd-j 364 root mem REG 8,18 8388608 524326 /var/log/journal/d59b94e79c8c4d78baaa487f78c7f5b1/user-1000@666512ad46e3412bb055fb811107893a-000000000062c409-0005e11333729c20.journal
php-fpm7. 696 root 4w REG 8,18 1456 64 /var/log/php7.4-fpm.log
unattende 821 998 gmain root 3w REG 8,18 113 524316 /var/log/unattended-upgrades/unattended-upgrades-shutdown.log
nginx 1016 root 2w REG 8,18 16384 393237 /var/log/nginx/error.log
nginx 1019 www-data 7w REG 8,18 4096 393267 /var/log/nginx/phplist-error.log
rspamd 1560 _rspamd 6w REG 8,18 7009 393282 /var/log/rspamd/rspamd.log

There are more of them, so I just removed some lines.

Services like ngins, rspamd, php-fpm are easy to stop, just do like following:

systemctl stop nginx.service

But what about systemd journal itself and kernel loggin? Do this:

systemctl stop logrotate.timer
systemctl stop unattended-upgrades.service
systemctl stop systemd-journald.service
systemctl stop syslog.socket

and they are gone!