It's not clear that would make anyone happy.

You might really want to track machines in your fleet, in a way that persists across reboots. Let's say you can access a machine remotely but you got all your ethernet cables tangled up, so you don't know which physical machine you SSHed into.

Or if you are being concerned about being tracked by a third party, you don't want this identifier to exist at all, even if it doesn't persist through reboots.

I agree there are other solutions in both cases.

So basically deleting the file as the last step before a shut down or reboot will work, is that correct?

Incorrect.

Machine IDs are stored in several places, some of which are not even files.

* http://jdebp.uk./Softwares/nosh/guide/commands/machine-id.xm...

They can be resurrected if not all storage locations are dealt with. Moreover, some systems use things like the SMBIOS product UUID.

* http://jdebp.uk./Softwares/nosh/guide/commands/setup-machine...

The correct approach is not deleting files.

* http://jdebp.uk./Softwares/nosh/guide/commands/erase-machine...

* https://lists.debian.org/debian-user/2019/03/msg00550.html

Thanks.

So at boot, one would run "erase-machine-id". Then create a random 30-character hexadecimal number. And then either set "the systemd.machine_id= kernel command line parameter" to it. Or pass it via "the option --machine-id= to systemd".

No.

    % system-control cat machine-id
    start:#!/bin/nosh
    start:true
    stop:#!/bin/nosh
    stop:envdir env
    stop:erase-machine-id
    run:#!/bin/nosh
    run:#Set up and tear down the machine ID
    run:envdir env
    run:setup-machine-id
    restart:#!/bin/sh
    restart:exec false      # ignore script arguments
    %

OK, thanks.

So "setup-machine-id". Does that generate a value that's unrelated to any preexisting versions, analogs, etc?

I ask because, when I deleted /etc/machine-id and ran "systemd-machine-id-setup", it generated a new machine-id by copying the D-Bus machine ID.

I'll test that.

Edit: OK, so I created a Debian VM, noted /etc/machine-id, deleted it, and rebooted. And found that it was still missing.

Running systemd-machine-id-setup generated a new machine-id from the D-Bus machine ID. And it was the same as the initial one.

But I also see in man machine-id:

> The machine-id may also be set, for example when network booting, by setting the systemd.machine_id= kernel command line parameter or passing the option --machine-id= to systemd. A machine-id may not be set to all zeros.

Does something like

dd if=/dev/urandom bs=1 count=16 | hexdump

Give you something that you can use?

Well, the machine-id of that Debian VM was ...

    38d05397c25548b4f4bda7751b5062

... and ...

    $ FOO=`cat /dev/urandom | tr -dc a-z0-9 | head -c${1:-30}`
    $ echo $FOO
      6we4gvnmx00w208ffty6i11m82rw6d

But I have no clue whether systemd would be happy with that. Maybe later I can test more.

Edit: Oops. Make that ...

    $ FOO=`cat /dev/urandom | tr -dc abcdef0-9 | head -c${1:-30}`
    $ echo $FOO
      b486935dbb9e9fe603328a19e2b5b4

Maybe use pwgen?

Something like:

    $ pwgen -1s 31
    qHfKU46H2RA2WUr0EZ1zBHfIBLKZKuT

I think that it needs to be hexadecimal. But not sure.

No worries. :)

Because then Google doesn’t have a persistent identifier to track you, of course.