machine-id
TLDR
View machine ID
$ cat /etc/machine-id
Generate new machine ID$ systemd-machine-id-setup
Check if ID exists$ test -f /etc/machine-id && echo "exists"
Compare machine IDs$ diff /etc/machine-id /var/lib/dbus/machine-id
SYNOPSIS
/etc/machine-id
DESCRIPTION
machine-id is a file containing a unique machine identifier established during installation or first boot. It's a 32-character lowercase hexadecimal string without hyphens.
The ID is used by systemd, D-Bus, and other services to uniquely identify the system. It should be stable across reboots but unique per machine.
FILE LOCATIONS
$ /etc/machine-id - Primary location
/var/lib/dbus/machine-id - D-Bus symlink
/var/lib/dbus/machine-id - D-Bus symlink
GENERATION
$ # Regenerate (for cloned systems)
rm /etc/machine-id
systemd-machine-id-setup
# Or manually
dbus-uuidgen --ensure=/etc/machine-id
rm /etc/machine-id
systemd-machine-id-setup
# Or manually
dbus-uuidgen --ensure=/etc/machine-id
CAVEATS
Should be unique per machine. Clone VMs need new IDs. Some software uses it for licensing. Not suitable as cryptographic secret.
HISTORY
machine-id was introduced by systemd to provide a standard machine identification mechanism, replacing various distribution-specific solutions.
SEE ALSO
systemd-machine-id-setup(1), dbus-uuidgen(1), hostnamectl(1)
