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OK, from the man page: > The /etc/machine-id file contains the unique machine ID of the local system that is set during installation. The machine ID is a singl

OK, from the man page: > The /etc/machine-id file contains the unique machine ID of the local system that is set during installation. The machine ID is a single newline-terminated, hexadecimal, 32-character, lowercase ID. When decoded from hexadecimal, this corresponds to a 16-byte/128-bit value. > The machine ID is usually generated from a random source during system installation and stays constant for all subsequent boots. Optionally, for stateless systems, it is generated during runtime at early boot if it is found to be empty. So if that works for "stateless systems", why can't all machines be "stateless systems"?

deleted 8y ago
[deleted]
dmurray 8y ago
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.
patrickg_zill 8y ago
So basically deleting the file as the last step before a shut down or reboot will work, is that correct?
- mirimir 8y ago
  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.
  - patrickg_zill 8y ago
    Does something like dd if=/dev/urandom bs=1 count=16 | hexdump Give you something that you can use?
    - mirimir 8y ago
      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
      - deleted 8y ago
        [deleted]
      - justinclift 8y ago
        Maybe use pwgen? Something like: $ pwgen -1s 31 qHfKU46H2RA2WUr0EZ1zBHfIBLKZKuT
        mirimir 8y ago
        I think that it needs to be hexadecimal. But not sure.
        justinclift 8y ago
        No worries. :)
- JdeBP 8y ago
  Incorrect. Machine IDs are stored in several places, some of which are not even files. * http://jdebp.uk./Softwares/nosh/guide/commands/machine-id.xml#STORAGE 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-id.xml#FALLBACKS 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-id.xml http://jdebp.uk./Softwares/nosh/guide/commands/erase-machine... * https://lists.debian.org/debian-user/2019/03/msg00550.html https://lists.debian.org/debian-user/2019/03/msg00550.html
  - mirimir 8y ago
    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".
    - JdeBP 8y ago
      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 %
      - mirimir 8y ago
        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.
tinus_hn 8y ago
Because then Google doesn’t have a persistent identifier to track you, of course.

deleted 8y ago

[deleted]

dmurray 8y ago

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.

patrickg_zill 8y ago

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

mirimir 8y ago
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.
- patrickg_zill 8y ago
  Does something like dd if=/dev/urandom bs=1 count=16 | hexdump Give you something that you can use?
  - mirimir 8y ago
    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
    - deleted 8y ago
      [deleted]
    - justinclift 8y ago
      Maybe use pwgen? Something like: $ pwgen -1s 31 qHfKU46H2RA2WUr0EZ1zBHfIBLKZKuT
      - mirimir 8y ago
        I think that it needs to be hexadecimal. But not sure.
        justinclift 8y ago
        No worries. :)
JdeBP 8y ago
Incorrect. Machine IDs are stored in several places, some of which are not even files. * http://jdebp.uk./Softwares/nosh/guide/commands/machine-id.xml#STORAGE 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-id.xml#FALLBACKS 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-id.xml http://jdebp.uk./Softwares/nosh/guide/commands/erase-machine... * https://lists.debian.org/debian-user/2019/03/msg00550.html https://lists.debian.org/debian-user/2019/03/msg00550.html
- mirimir 8y ago
  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".
  - JdeBP 8y ago
    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 %
    - mirimir 8y ago
      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.

tinus_hn 8y ago

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