Dr. Nikolaus Klepp wrote:

> The process is triggered by one of the many raceconditions introduced in
> systemd. If you can, get rid of systemd, install devuan or exegnulinux or
> antix or ....

no need to do so. just install 
ii  sysv-rc                               2.88dsf-59.9                               
all          System-V-like runlevel change mechanism
ii  sysvinit-core                         2.88dsf-59.9                               
amd64        System-V-like init utilities
ii  sysvinit-utils                        2.88dsf-59.9                               
amd64        System-V-like utilities

trash systemd-sysv and reboot

if you keep systemd-sysv add in /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT ..... init=/lib/sysvinit/init

and update-initramfs


but it could be also a disk issue or unclean fs - probably you don't use
ext4 and/or root is setup to remount ro on error

boot from rescue and fsck

regards