/dev/mem isn't necessarily available. Recently, I've encountered arm64
systems that didn't provide raw memory access via /dev/mem. Instead,
let's use /dev/kmsg since we don't support systems w/o it anyway.
Description=Test for PrivateDev=no
[Service]
-ExecStart=/bin/sh -x -c 'test -c /dev/mem'
+ExecStart=/bin/sh -x -c 'test -c /dev/kmsg'
Type=oneshot
PrivateDevices=no
Description=Test for PrivateDev=yes
[Service]
-ExecStart=/bin/sh -c 'test ! -c /dev/mem'
+ExecStart=/bin/sh -c 'test ! -c /dev/kmsg'
Type=oneshot
PrivateDevices=yes