EmonPi crashes running OS on SSD

Hi @borpin, the df -h shows the following:

Filesystem      Size  Used Avail Use% Mounted on
/dev/root        20G  2.3G   17G  13% /
devtmpfs        481M     0  481M   0% /dev
tmpfs           486M     0  486M   0% /dev/shm
tmpfs           486M  520K  485M   1% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           486M     0  486M   0% /sys/fs/cgroup
tmpfs            40M  6.6M   34M  17% /var/lib/openhab
tmpfs           1.0M     0  1.0M   0% /var/lib/dhcpcd5
tmpfs           1.0M  8.0K 1016K   1% /var/lib/dhcp
tmpfs            50M  6.2M   44M  13% /var/log
tmpfs           1.0M     0  1.0M   0% /var/tmp
tmpfs            30M   36K   30M   1% /tmp
/dev/mmcblk0p3  3.8G  237M  3.4G   7% /home/pi/data
/dev/mmcblk0p1   60M   22M   39M  37% /boot
/dev/sda2       897G   79M  851G   1% /mnt

So, /var/log at 6.2MB. But when I do du /var/log/ -h, I get 71MB!

0       /var/log/supervisor
4.0K    /var/log/mosquitto
8.0K    /var/log/logrotate
8.0K    /var/log/openhab
4.0K    /var/log/mysql
4.0K    /var/log/apache2
4.0K    /var/log/redis
4.0K    /var/log/emonpilcd
65M     /var/log/journal/5e3a8d5cbaff427898fd4b9ec446e38e
65M     /var/log/journal
71M     /var/log/

Another topic is that I have noticed the temp files located in /var/cache/man cleaning is failing because the system is read-only. Could this be a source of problems? At this time all files in /var/cache/man are 1.9MB only (du /var/cache/man/ -h).

-Extract of journalctl:

Feb 16 20:02:37 emonpi systemd[1]: Starting Cleanup of Temporary Directories...
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/tr/cat1): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/tr/cat8): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: unlink(/var/cache/man/tr/index.db): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/tr/cat5): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: unlink(/var/cache/man/tr/CACHEDIR.TAG): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: utimensat(/var/cache/man/tr): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/tr): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/cs/cat1): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/cs/cat7): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/cs/cat8): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: unlink(/var/cache/man/cs/index.db): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/cs/cat5): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: unlink(/var/cache/man/cs/CACHEDIR.TAG): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: utimensat(/var/cache/man/cs): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/cs): Read-only file system
Feb 16 20:02:37 emonpi systemd-tmpfiles[6924]: rmdir(/var/cache/man/ru/cat1): Read-only file system