SYSTEMD-BOOT-SYSTEM-TOKsystemd-boot-systemSYSTEMD-BOOT-SYSTEM-TOKEN.SERVICE(8)
NAME
systemd-boot-system-token.service - Generate an initial boot loader
system token and random seed
SYNOPSIS
systemd-boot-system-token.service
DESCRIPTION
systemd-boot-system-token.service is a system service that
automatically generates a 'system token' to store in an EFI variable in
the system's NVRAM and a random seed to store on the EFI System
Partition ESP on disk. The boot loader may then combine these two
randomized data fields by cryptographic hashing, and pass it to the OS
it boots as initialization seed for its entropy pool. The random seed
stored in the ESP is refreshed on each reboot ensuring that multiple
subsequent boots will boot with different seeds. The 'system token' is
generated randomly once, and then persistently stored in the system's
EFI variable storage.
The systemd-boot-system-token.service unit invokes the bootctl
random-seed command, which updates the random seed in the ESP, and
initializes the 'system token' if it's not initialized yet. The service
is conditionalized so that it is run only when all of the below apply:
o A boot loader is used that implements the Boot Loader Interface[1]
(which defines the 'system token' concept).
o Either a 'system token' was not set yet, or the boot loader has not
passed the OS a random seed yet (and thus most likely has been
missing the random seed file in the ESP).
o The system is not running in a VM environment. This case is
explicitly excluded since on VM environments the ESP backing
storage and EFI variable storage is typically not physically
separated and hence booting the same OS image in multiple instances
would replicate both, thus reusing the same random seed and 'system
token' among all instances, which defeats its purpose. Note that
it's still possible to use boot loader random seed provisioning in
this mode, but the automatic logic implemented by this service has
no effect then, and the user instead has to manually invoke the
bootctl random-seed acknowledging these restrictions.
For further details see bootctl(1), regarding the command this service
invokes.
SEE ALSO
systemd(1), bootctl(1), systemd-boot(7)
NOTES
1. Boot Loader Interface
https://systemd.io/BOOT_LOADER_INTERFACE
systemd 245 SYSTEMD-BOOT-SYSTEM-TOKEN.SERVICE(8)