I had this issue with some systems, but not all. Since these systems
have been upgraded from Jessie to Stretch, not all of them have been
changed by apt to what I call full-systemd.
After being bitten by this issue, I have learned how to predict which
will fail and which will not. If the output of 'file /sbin/init' is
"*/sbin/init: symbolic link to /lib/systemd/systemd*", then apache2 will
start after the upgrade.
However, if the output is similar to "*/sbin/init: ELF 64-bit LSB
executable, x86-64, version 1 (SYSV), dynamically linked, interpreter
/lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32,
BuildID[sha1]=4a7d2a34f4f122bf7c614e277f521789f675764b, stripped*", then
apache2 will fail to start.
So currently, the apache2 upgrade absolutely requires the systemd init
system, but not all systems have that in place. For reasons known only
to apt, the Stretch upgrade path has not led them there.
Dale Schroeder
