/etc/machine-id is mounted as tmpfs and is non-persistent

[Yannic Schröder]

Raspbian Jessie Lite 2017-04-10 boots up using a temporary machine-id in /etc/machine-id mounted as tmpfs:

pi@raspberrypi:/etc $ mount | grep machine
tmpfs on /etc/machine-id type tmpfs (ro,mode=755)

pi@raspberrypi:/etc $ dmesg | grep machine
[ 1.544257] systemd[1]: Initializing machine ID from random generator.
[ 1.547164] systemd[1]: Installed transient /etc/machine-id file.

For me this results in etckeeper failing to initialize:

pi@raspberrypi:~ $ sudo etckeeper init
chmod: changing permissions of ‘machine-id’: Read-only file system

It should instead generate a persistent machine-id that stays the same after rebooting.

This problem is also already discussed on StackExchange:
https://raspberrypi.stackexchange.com/questions/66364/constantly-changing-etc-machine-id