systemd-firstboot are great for systems using systemd,
/etc/machine-id is not a systemd file, despite the tag. It is also used on systems that do not use systemd. So as an alternative, you can use the
rm -f /etc/machine-id
As mentioned by Stephen Kitt, Debian systems may have both a
/etc/machine-id and a
/var/lib/dbus/machine-id file. If both exist as regular files, their contents should match, so there, also remove
and re-create it:
This last command implicitly uses
/var/lib/dbus/machine-id as the file name and will copy the machine ID from the already-newly-generated
dbus-uuidgen invocation may or may not already be part of the regular boot sequence. If it is part of the boot sequence, then removing the file and rebooting should be enough. If you need to run
dbus-uuidgen yourself, pay attention to the warning in the man page:
If you try to change an existing machine-id on a running system, it will probably result in bad things happening. Don't try to change this file. Also, don't make it the same on two different systems; it needs to be different anytime there are two different kernels running.
So after doing this, definitely don't continue using the system without rebooting. As an extra precaution, you may instead reboot first into rescue mode (or as you suggested, boot from a live USB stick), but from my experience, that is not necessary. Bad things may happen, but the bad things that do happen are fixed by the reboot anyway.